The Liberal Democrats have put the environment at the centre of our thinking ever since the party was born, our commitment is based on deeply held beliefs, not on the latest focus groups.

Our prosperity, our security, our quality of life, the very sustainability of the planet, depend on our society’s attitude towards the environment. James Lovelock’s recent warning that global climate change may have reached a point of no return should make every politician stop and think.

The challenge, then, is not to make the rhetorical case for taking the environment seriously. We’ve had enough hot air and hand wringing. The real challenge is to transform that case into practical political steps which make a material difference to the sustainability of our shared environment.

To do so, we must develop specific proposals which change individual behaviour while not unduly threatening the quality of life to which people have become accustomed. We must set out in bold terms how environmentally responsible behaviour increases, rather than decreases, the quality of life of everyone. When the Clean Air Act was introduced it was held to be an act of economic vandalism, killing off smokestack industries and throwing thousands of people out of work. Yet soon the absence of the choking smog which had overshadowed the lives of millions in our great cities was held to be one of the greatest advances in the nation’s quality of life ever introduced.

We must be far more imaginative in explaining how changes in individual behaviour can produce a win-win outcome for both the environment and consumers. Energy efficiency measures, which cut carbon emissions, also provide enormous financial savings for families. As leader, I will be unveiling an action plan for a significant boost to energy saving technologies and the provision of incentives to households to encourage the necessary changes at home. What is true for households, also applies to businesses. The Carbon Trust recently set out a detailed analysis of the way in which the costs of energy efficiency measures implemented by manufacturers can be recouped through lower running costs in a surprisingly short space of time.

The tax system and user charges must be used to create incentives to change behaviour. Environmental concerns must be centred in the Treasury, not regarded as some sort of departmental add-on. We’ll create an Environmental Incentive Programme in the Treasury to see how within the same overall tax envelope, incentives for good environmental behaviour can be built into the tax system. Individual behaviour is more likely to change in the right direction if there is a clear material incentive to do so, as well as a positive effect on the environment. There is a case to consider the expansion of road charging systems, as long as the revenues are clearly dedicated to improving public transport alternatives.

Incentives must exist to discourage unnecessary car use rather than an overnight attempt to price travellers out of their vehicles by pushing the price of fuel beyond their reach. I will want to ensure that our party’s position on this is both workable and credible.

I will also be calling for new ideas to provide more information to individuals and households so that they can assess for themselves the environmental impact of their actions. Airline tickets should provide information on the carbon emissions of each flight, and of each type of aircraft. The age of cheap air travel has allowed millions of Britons to travel abroad. But aviation is emerging as one of the most harmful sources of carbon emissions.

The development of individual or household carbon accounts, if the technology eventually allows, might have a significant effect on everyday behaviour. The principle is already being put into practice for businesses in the EU’s carbon emissions trading system. I want the Liberal Democrats to be at the forefront of applying the same approach, if workable, to the rest of us.

Underpinning all of this has to be a new international agreement on carbon dioxide emissions to tackle climate change. Our party policy is based on the twin principles of contraction and convergence – we have to ensure that there is international agreement on contracting our carbon dioxide emissions and delivering an equitable convergence of emissions for all nations, developed and developing. It is unrealistic to expect developing countries to be responsible about their emissions if we do not reduce ours – so as an incentive to countries like China and India to adopt renewable energy, we have to show that we are prepared to reduce our emissions by doing the same.

I am clear that Mr Blair’s apparent determination to boost nuclear energy as a solution to the problem of carbon emissions is flawed. The costs of constructing and decommissioning nuclear plants are astronomical. The public is already having to bear the heavy costs of nuclear waste disposal. By pressing ahead with an expansion of nuclear energy generation, the Government could be saddling future generations with a permanent burden of vast public subsidies which could be much more effectively deployed to boost other forms of energy generation. Mr Blair’s decision to gamble all our futures on only one, enormously expensive, form of energy generation is enormously risky.