If Scotland votes 'Yes' next week, recrimination will be surely followed by deep, profound changes to rUK's political system.

It is 100 years since the Irish Home Rule Bill reached the statute book, only to lie there dead on the mortuary table of British imperial history. The Irish war of independence consigned it to the crematorium. If the SNP sticks to its timetable for separation, Scotland will become an independent nation in March 2016, on the eve of Ireland's centenary celebrations of the Easter Rising, the bloody rebellion that signalled the start of the end of the Union of Great Britain and Ireland.

Is next week's referendum vote in Scotland simply a further stage in the historical disintegration of the United Kingdom? That is certainly the view of radical sceptics of 'Ukania', the political heirs of Tom Nairn's 1970s new left generation who now line up alongside the SNP in seeking independence. But it is also the view of less obviously partisan observers, such as the great Scottish historian Tom Devine, for whom the ties that bound the union – protestant unionism, imperial trade markets, British army regiments, and working class solidarities – have all gradually become unstitched. Fatalist commentators echo this sentiment: it is pointless, they argue, to blame the leaders of the Better Together for the weakness of the No campaign, for they sit atop a crumbling edifice.

Gordon Brown's evocation of a quasi-federal, 'home rule all round' future for the United Kingdom is a thunderous riposte to these claims. It may be too late in the day to save the union, so tight has the race become. But it is an intervention premised on two important insights that merit further explication. The first and most obvious is that the No campaign should always have articulated a positive, constructive account of Scotland's future, not simply set out reasons why separation would damage the country's economy and threaten its welfare state. One reason why all the energy has flowed to the Yes campaign is that the Better Together campaign, despite its best efforts, has found it hard to shift off the status quo. It is difficult to animate a static political position – hence the new emphasis on a rapid timetable for greater devolution of powers to the Scottish parliament (a full account of what an extensive 'devomore' agenda might consist of can be found in IPPR's publications here).

The second insight is that the debate about Scotland's future could not be conducted on the terrain of Britishness. The referendum has been about Scotland, not Britain. As Brown knows to his own cost, Britishness now has limited cultural and civic purchase on Scottish voters; reduced to its instrumental dimensions, it becomes simply an economic argument. Supporters of the union have to articulate a positive argument – cultural and political, as well as economic – for Scotland's future in the union, not for the union per se. They are surely right that a grim future, rather than vital independence, awaits a small country that shares a currency with its larger neighbours without having any control over its monetary or fiscal policy, as Ireland has found. But economic anxiety has thusfar not proved strong enough to counter the demands for self-government and popular control that the Yes camp has harnessed.

The Labour party in Scotland – easily the most small-c conservative of the unionist parties on the question of further devolution – has reached for its own traditions to bring alive the antiseparatist case. It evokes the commonalities of interest among the working people of the nations of the UK, and the hallowed names of Kier Hardie and Nye Bevan. But this is a political language too redolent of an industrial past to have much purchase on the future. The social union, and its embodiment in the state pension and a shared NHS, in particular, remains a vital wellspring of what makes Great Britain worth living in, but couching it in terms of Labour movement heroes and traditions has proved very ineffective.

Moreover, if John Curtice is right, much of the late surge to the Yes campaign has come from those who didn't vote in 2011, and not simply disaffected Labour voters. This suggests that at the heart of the success of the independence movement is the widespread desire to exercise self-government and to draw power further down towards the people of Scotland. Older voters may be anxious about their pension and the NHS, but a wide swathe of Scottish society wants a new and more democratic political order.

Similar sentiments abound in England, and whatever the outcome of the referendum next week, a major restructuring of the constitutional order of the UK is on the cards. England will demand its own devolution settlement, not least to its northern cities. 'English votes on English laws' is now much more likely for the House of Commons, as is a quasi-federal reform of the House of Lords. If Scotland does stay in the union, any rapid agreement on new powers for its parliament cannot take English opinion for granted and leave undisrupted the status quo south of the border.

The question is how this process of renewing the democratic settlement takes place. Westminster parties are not trusted to lead the process, but nor can elected politicians be excluded from it. It must be a pluralist, multidimensional affair if it is to succeed – rather like that undertaken in Ireland in its attempt to restore trust in a broken, post-crash polity. It will require new forms of political leadership as much as citizen engagement.

The panic that has spread through London in recent days is eerily redolent of those moments in British history when colonial territories have broken away: indifference in London followed by incomprehension and anger – and then botched compromise. But as importantly, these major moments – the American and Irish wars of independence in particular – also led to significant restructuring and realignment of the Westminster party system. If Scotland votes 'Yes' next week, recrimination will be surely followed by deep, profound changes to rUK's political system. The crisis (and it surely merits that description) will be greatest for the Labour party, but none of the parties will emerge from it unscathed.