Dear Mr Khan,

You will have a stacked in-tray of challenges on your first day in City Hall – from the housing crisis to transport – but one of the fundamental issues that will determine the health of London’s economy is the environment.

Quality of life is a key determinant of how attractive the capital is to world-class talent, and to improve it we need action to tackle pollution, lower energy bills and recover London’s ever-shrinking green spaces.

Reclaiming London’s heritage of municipal renewal

The story of how London became and remained a world leading city is also the story of how it overcame environmental problems.

In the early 1800s, London was experiencing unprecedented economic and population growth, leading to a raft of health and social problems. In response, the Victorians instigated a programme of municipal renewal in which new parks, sewers and local institutions enabled significant progress to be made on overcoming London’s social and environmental problems.

More than 100 years later, you will inherit a city that has made great strides in becoming cleaner, greener, and more prosperous. But you will also inherit one of the least liveable cities in Europe, in which illegal levels of air pollution kill thousands of citizens every year; where one in 10 people can’t afford their energy bills; and where recycling levels are the poorest in the country.

The virtuous circle – from environmental sustainability to economic progress – is breaking down, and the evidence is all around us.

Air, homes and energy

We are once again at a crossroads. Either London invests in making the city more liveable and green, cementing and maintaining its global leadership in a changing world, or it will continue to see its quality of life deteriorate, with serious knock-on effects to the engine room of Britain’s economic growth.

The needs of a rapidly growing population – set to rise beyond historical records – will add to the challenge. As mayor you will need to harness the talent, technologies and business models that will drive decarbonisation and ensure environmental sustainability.

It is clear that London’s air has been lethal and illegal for some time now, causing the equivalent of 9,400 deaths in 2010. Air pollution is now responsible for more ill-health than obesity or alcohol, and is second only to smoking; it is caused primarily by London’s increasingly congested road traffic.

A growing population – set to exceed 10 million by 2031 – will make the air pollution problem even worse.

More people also means more homes, and, as Lord Kerslake’s London Housing Commission has shown, the capital is already in the grips of a housing crisis: London needs to build 50,000 homes per year up to 2030 in order to house its growing population. This could mean the loss of even more of the natural environment – development ate up an area of green space equivalent in size to Hyde and Battersea parks between 2009 and 2012 alone.

A growing population will also have significant energy demands, potentially slowing the pace at which London can reduce its greenhouse gas emissions. In fact, progress is already stalling, which is partly down to an energy market that overcharges millions of customers and underinvests in renewables. This will make it harder for London to provide energy to its growing population.

Creating a global green city

Last month, the IPPR published our London: Global green city report, which shows how the new mayor could overcome these problems by enacting an integrated programme of investment in London’s social, economic and environmental wellbeing.

The immediate priority is to combat London’s transport problems. As mayor you will need to take swift and bold action to combat the twin afflictions of air pollution and congestion. You should mandate Transport for London to assess the viability of combining and extending the existing and planned charging zones to create a Clean Air Zone that charges drivers for the amount of emissions and congestion they cause. This proposal has gained the support of a number of key groups in London, and the large revenues it would create could be reinvested in improving transport for all Londoners.

On energy, you should expand your plans for a London energy company by establishing Energy for London, a fully licensed supply company providing electricity and gas for Londoners that builds on the successful examples of Nottingham and Bristol city councils. Its revenues could then be channeled into supporting local renewable energy and increasing the efficiency of London’s homes as part of a strategy to help people reduce their energy use and keep them on the lowest tariffs.

Keeping London in the global top-flight

Already, the 21st century’s most successful cities are those whose development models integrate environmental priorities into all areas of city planning, from the economy to communities. You need to bring London up to speed, and should set an aim to make London a world leader in making the city greener, cleaner and more efficient – a ‘global green city’.

A good start would be to arrest the decline in London’s green space. In doing so, you should appoint a green infrastructure commissioner and establish London as a national park city, providing an overall framework for increasing biodiversity and green space.

And finally, your role as mayor comes at a crucial moment in history: winning a second term would mean you would be in power for just under a quarter of the time that remains until 2050, when the world must be approaching decarbonisation. This is an enormous responsibility – but one that presents you with a unique opportunity to turn London into one of the cleanest, greenest, most prosperous cities in the world – a global green city.

Yours sincerely,