Tim Bale, a leading academic expert on the Conservative party, argues that the death of the Conservative left has dire consequences for the party's electoral prospects, the future of the Coalition and the wider political landscape.

There is little doubt that, between the early 1950s and early '70s, the centre of gravity of the Conservative party was well to the left of its position today.

The party under Churchill, Eden and Macmillan had its fair share of right-wingers of course. Some were determined to hang on Britain's imperial role; others were obsessed with the dangers posed by 'coloured' immigration and European integration; a fair few were hangers and floggers; and probably many more would have been more than happy to humble the unions, and reduce red tape, taxes and spending.

But the 'solid centre' of the parliamentary party, as well as many of its leaders at the time, was pretty much convinced that the only way that the Conservative party would be permitted to govern the country was by preserving full employment via cheap money and counter-cyclical spending, by keeping the trade unions sweet, and by maintaining and, where the shoe pinched, even expanding the welfare state. By the late 1950s, as the economy began to run into trouble and the government was humiliated over Suez, there was even grudging (if heavily qualified) acceptance that Britain should, firstly, think about borrowing the quasi-corporatist techniques that seemed to be serving its continental rivals so well and, secondly, that it should finally face up to the end of empire by getting shot of its remaining colonies, imposing sensible controls on Commonwealth immigration, and admitting that the nation's destiny lay in Europe.

Pretty much all of this became - more by default than by design perhaps - the credo of the post-war Tory left, although other touchstones were adopted as the 1950s turned into the '60s and the '60s turned into the '70s. For instance, firm control of immigration was to be balanced by anti-discrimination legislation, while the diehard defence of Britain's divisive secondary school system was to be abandoned in favour of comprehensives.

There were of course nuances and differences, not least (but not exclusively) when it came to the role and limits of the state. Most of those on the left, liberal and progressive wings of the party saw no real alternative to the mixed economy. Yet many of them - particularly as they looked back in opposition at their 13 years in government between 1951 and 1964 - came to believe that the state should be leaner and fitter, and that the unions had to be faced down and made subject to legal sanction rather than continually appeased.

Ted Heath led a party which was largely (though never completely) in the hands of so-called progressive, 'One Nation' Tories. Yet he came into government promising to strengthen Britain's borders, re-establish its military presence 'east of Suez', and above all to implement what he and his colleagues - some with eager anticipation, some with no little anxiety - clearly regarded as a radical, even revolutionary programme which would shrink the state and succeed where Labour had failed in taming the trade unions.

When it came to the crunch, however, the leadership cut short its flirtation with free market capitalism and essentially reverted to Macmillanite type. 'Lame duck' companies were rescued with public subsidies; incomes policies were reintroduced; recalcitrant unions, rather than being brought legally to heel, were bought off with inflation-busting increases; spending and interest rates were manipulated to bring down an alarming increase in joblessness; tens of thousands of Ugandan Asians were given sanctuary at a stroke; and no more was said about 'east of Suez' as the UK at last managed to persuade the EEC to allow it to join the club.

Although what Macmillan himself famously referred to as 'events, my dear boy, events' were clearly crucial, just as important was the fact that the party was led and, at least in parliament, largely populated by people who had joined men from all classes in fighting in one or even two world wars - people who were scarred by the landslide defeat inflicted by Labour in 1945, and who were acutely conscious that, for more than a decade, the UK had been lagging behind other European countries which practised a more coordinated form of capitalism. As a result, they could not ultimately accept the price of a return to more 'orthodox', laissez-faire economy, namely prioritising the battle against inflation (and the unions) above everything else and, as a consequence, allowing unemployment to rise to levels that had not seen since the 1930s and which many regarded as both electorally unfeasible and morally indefensible.

In and of themselves, the Heath government's U-turns might not have proved fatal to the Tory left. That they did so was down to the fact that - especially when it came to the economy - they made things worse rather than better. Yet Tory progressives might have retained control of the party after the twin election defeats in 1974 if they had handled the aftermath more adroitly. By no means everyone who voted for Thatcher when she was brave enough to challenge Heath for the leadership believed in the alternative she was offering - but at least she was offering an alternative, and the opportunity for the party to regain its dignity and distinctiveness.

Thatcher's victory in the leadership contest was a stunning surprise for the Tory left, but it was not initially recognised as the devastating blow it eventually became. Many, maybe even most, of her erstwhile cabinet colleagues convinced themselves that Thatcher would either prove a flash in the pan or at the very least be tamed by a combination of the centrism of the British electorate and the prosaic realities of power.

They also believed that her right-wing radicalism didn't really run that deep. This was not necessarily an unreasonable assumption to make given her fairly unremarkable record as Heath's secretary of state for education. But it failed to take full account of the fact that Thatcher not only lacked the direct experience of war that was the wellspring of many a progressive's sense of consensual noblesse oblige but (perhaps because, unlike so many of them, she was a product of the provincial grammar-school-going and shop-keeping classes) also fully shared the anti-union, anti-collectivist and anti-inflationary prejudices of many ordinary members of her party. Her opponents also underestimated her determination, demonstrated long before she made it into Number 10, to hand over the key policy portfolios to fellow true-believers, and the rapidity and ruthlessness with which she shunted those she saw as irredeemable patricians to the sidelines.

What happened to the Tory left after 1974, then, was not a losing out to slow-acting evolutionary competition from necessarily better-adapted competitors, but the political equivalent of being hit by a massive meteorite. Some survived the immediate impact, but in most cases not for very long. After 1979, a combination of Thatcher's electoral success and generational replacement within the parliamentary party - plus the increasingly poisonous politics of Europe - meant that even those progressives whose talent made them individually indispensable (Ken Clarke being the paradigmatic example) quickly found themselves fewer and farther between.

The Conservative party may have dumped Thatcher in 1990, but it did not dump Thatcherism. Indeed, by 1992 it was well on the way to being the almost fully Thatcherite entity it is today. There are of course shades of grey, but the main point of ideological contention is clearly between, on the one hand, a substantial minority (possibly bigger in the party in the country than in the party in parliament) who would like to see the Tories adopt a stronger 'faith, flag and family' stance and, on the other, those who consider themselves social liberals - more because they grew up in a multi-ethnic country in the wake of the sexual revolution of the 1960s and '70s than because of any nostalgic affinity with what, at the time, was the Conservative party's progressive avant-garde.

Inasmuch as a Tory left can currently be said to exist - beyond, that is, the odd marginal minister and senior backbencher, a few defunct or one-man-and-a-dog ginger groups, a tiny bunch of bloggers and a sprinkling of self-styled thinktanks - it is hardly surprising that 'post-materialist' issues are where it focuses its attention. Locked out of any real influence on the economy, public services, immigration and Europe, what remains of non-Thatcherite 'progressive' Conservatism consoles itself by pushing 'social' causes such as sexual and racial equality and drumming up enthusiasm for the Big Society. Perhaps they convenient forget that Thatcher, for all her support for law and order and immigration control, was never censorious about sex and would have no trouble whatsoever buying into the idea that as the state is rolled back, individuals, families and volunteers will not only fill the vacuum but fill it better.

To many on the Tory right, the near disappearance of the Tory left is a cause for celebration. To them (as to Thatcher and her John the Baptist, Keith Joseph), the party's post-war progressives presided over decades of 'fudge and mudge' during which the Conservatives did themselves and the country no favours at all by allowing Labour to determine the limits of the politically possible. Their passing - and their failure to pass on any but the weakest of torches to anyone coming after - signals the triumph of home-truth Toryism.

Arguably, however, the paucity of progressives in today's Conservative party is a source of weakness rather than strength. Back at the end of the 18th century, Edmund Burke reminded reactionaries that: 'A state without the means of some change is without the means of its conservation.' The same goes for a political party. Without a genuine balance of forces that ensures the presence of people prepared to challenge the prevailing wisdom, a damaging groupthink can develop, blinkering the majority that buys into it into believing that there is no alternative even when, objectively speaking, the course they are following is taking them nowhere.

This, after all, was the situation in which the Conservative party found itself by the mid-1970s. But it was able to reinvent itself precisely because its right wing (and the rumbling critique of its supposed 'surrender' to socialism) never entirely disappeared. Eventually, it finally found in Margaret Thatcher the figurehead it needed to mount a challenge to the contemporary common sense.

There were some who believed that David Cameron would play the same role (albeit in reverse) some 30 years later. Thatcherism, it seemed, had outlived its usefulness. Having met the country's needs brilliantly in the 1980s, it was already looking dated by the '90s, and was positively clapped-out by the '00s. It appeared the Tory right had had its day, just as the Tory left had done by the mid-'70s. It was time for a man whom many convinced themselves was the heir not so much to Blair but to Macmillan. It wasn't just Cameron's ability to communicate across classes and his evident social liberalism. It was the endlessly avowed enthusiasm for the centre ground, the unambiguous support for the NHS, the repeated assurances that public sector workers weren't parasites but doing a valuable job, the refusal to join the clamour to bring back grammar schools, and the turning down of the volume and the change of tone on law and order immigration.

Yet, for all this, Cameron, as leader of the opposition, never really had any of the big arguments with his party that someone driving genuine change needs to have. In part, this was because he didn't believe in picking fights as a strategy. But the underlying reason was because, scratching beneath the surface appearance of centrism that he initially believed was vital to securing an election victory, Cameron was and is ultimately no less a Thatcherite than the vast majority of his colleagues. This became obvious even before May 2010 when he reverted to orthodox type in response to the domestic consequences of the global economic crisis.

Because there was no transformation towards post-Thatcherism, let alone pre-Thatcherism, Cameron as prime minister is now faced with a party in parliament and in the media which borders on the delusional - unable to accept that simply swallowing more and more of the medicine once prescribed by their heroine won't do the job, nor that they are still too far away from where most voters see themselves to win the kind of victory that will allow them to govern on their own.

In a proportional representation electoral system, this wouldn't matter: the Conservatives, like a number of centre-right parties in Europe, could team up with a populist party and govern, either as a minority with a confidence and supply arrangement or in a full-blown coalition. But in a first-past-the-post system, the Tories have no alternative but to try to pull off a plurality win. In the absence of a significant lead over Labour in terms of competence, party unity, economic performance or leadership (a lead which at the moment, Cameron versus Miliband excepted, the Tories do not enjoy), this can only be achieved by the Conservative party positioning itself reasonably near the point on the left-right continuum where the bulk of the electorate locates itself.

Despite the efforts of a few outspoken (and well-resourced) realists like Lord Ashcroft to provide polling evidence for staying on (or at least near) the centre ground, this cannot and will not happen unless there are enough people in the party itself who are willing to make a positive argument for a different kind of Conservatism to the variant that currently rules the roost. Ideologically, the Tory left would be ideally placed to fulfil that role. Sadly - and possibly fatally for the party's chances at the next election and beyond - it is nowhere near strong enough to do so.

The weakness of the Tory left may also account for an even more pressing problem, namely the difficulties the Conservative party is currently experiencing in coalition. The gap between the Tories and the Lib Dems has proved much bigger than creative thinkers on the Conservative side, such as Nick Boles, hoped that it would be - precisely because the number of his colleagues willing and able to reach across it is so small. Cutting taxes and the deficit was no problem for most of Cameron's troops, but so many of them clearly believed - and continue to believe - that the government should go even further and even faster. And as for the Liberal Democrats' enthusiasm for corporation tax, employment protection, protecting the NHS, constitutional reform and a more pragmatic line on the EU - enough said. All this might have been different had the Tory left not shrunk to the extent that it has over the last two or three decades, thereby leaving the Conservative party bereft of voices prepared to stress what potentially unites rather than hopelessly divides the coalition partners.

Ironically, one reason why the Tory left failed to reproduce itself was the fact that the party's drift to the right became, after a while, self-reinforcing and self-perpetuating. Young would-be politicians who might once have been comfortable as Conservatives concluded that there was simply no point in them joining such a 'nasty party' - assuming they even thought about the possibility at all. Some gave up politics altogether. Others, like Nick Clegg, joined the Lib Dems. In May 2010, they set aside the concerns of their colleagues who hadn't signed up to their 'Orange Book' smaller-state liberalism and grabbed a once-in-a-political-lifetime opportunity to bring the two parties closer together. For a few short months, it looked like they may have succeeded - and, had there been more Conservatives ideologically willing and able to forge what would have been a truly historic compromise, perhaps their success might have lasted. Ultimately, however, it is difficult, if not impossible, to build a bridge from just one side of the shore.

This article is an edited version of a longer essay which appears in issue 19(2) of Juncture, IPPR's quarterly journal of politics and ideas. The full version is available for download.