Nicky Gavron: We need a new version of the Clean Air Act

Legislation can make a difference - a big difference. This month is the 50th anniversary of the Clean Air Act. Faced, in the early 1950s, with the crisis of air pollution - the Great London Smog of 1952 killed 4,000 people - the Government of the day applied mandatory smokeless zones to towns and cities. Within just three years the use of coal disappeared from our cities and Londoners breathed easy.

Today we face an even worse crisis. Climate change isn't some theoretical concept, it is happening here and now. Cities are massive producers of carbon dioxide, mainly from the energy used in buildings, not traffic. Climate change is now the greatest political imperative facing the planet.

And people understand the problem. Polls show a growing concern about climate change. And, just as they are turning to fair-trade goods in supermarkets, many people want to feel part of a solution to climate change, rather than part of the problem. What is missing is a progressive measure that people can rally around.

Just as we needed a Clean Air Act - proactive and mandatory legislation promoting urgent change - so today we need a Low Carbon Act. A number of radical suggestions are being floated that could be wrapped up in such legislation. A clear leader is the proposal for a rolling programme of low carbon zones, aimed at dramatically improving the energy efficiency of all our buildings - our public and commercial premises and especially our homes.

British homes account for a quarter of total energy use and carbon emissions, rising to 44 per cent in London. The vast majority of these emissions could be tackled through improvements in their energy performance. The Government admits in the Energy Review that current programmes are just not up to the task of cutting energy supplies or using supply more efficiently.

One of the boldest proposals in the review is to move in 2011 to a model in which utility companies would be rewarded for reducing carbon emissions, encouraging them to market heating, lighting and power in the most energy-efficient way practicable. But this will not be a regulatory requirement. Mandatory low carbon zones could complement such a model, expanding and accelerating its effectiveness through regulation. These zones could be rolled out across the country incrementally, just as the smokeless zones of the 1950s were, with relevant authorities and devolved administrations declaring an area a low carbon zone, inviting private sector partners to deliver the actual service.

Within a specified time, all properties within the zone would be required to be up to a minimum rating of energy efficiency. Focusing zones around neighbourhoods has great advantages: economies of scale, scope for combined heat and power plants and a guarantee that no fuel-poor household falls through the net - a serious problem for current programmes.

Energy-saving schemes would focus on the whole property, covering insulation, double-glazing, low-energy lighting and efficient heating, electricity systems and appliances. Householders could be offered the opportunity to generate their own electricity through solar panels or micro wind turbines, becoming energy producers, not just consumers.

Many of the measures will pay for themselves through lower bills. The central idea would be for energy suppliers to meet the up-front costs, effectively making a loan to the householder, which is paid off on their energy bill over time and at no extra cost.

Alternatively, "green mortgages" could enable homeowners to roll the cost of improving their homes' energy performance into mortgage payments, with the extra repayments offset by lower bills. This is not unprecedented - since 1982, everyone selling a home in San Francisco has has had to undertake energy efficiency measures. As a result green mortgages are commonplace.

London has been given a climate change duty under new powers announced last week and the London Climate Change Agency could pilot low carbon zones now. A White Paper on devolved powers for local authorities including, I hope, the power to tackle climate change is expected in the autumn. Potentially, we stand on the edge of the most radical reform of local government for decades. The time is right for a new era of municipal enterprise.

A Low Carbon Act, in the radical spirit of the Clean Air Act, could halve the amount of carbon for which buildings are responsible and help tackle the greatest challenge facing our planet without recourse to nuclear power.

Nicky Gavron is deputy Mayor of London