Election 2010: Party promises | Environment | Greenpeace's verdict

The Liberal Democrats have the progressive lead

Labour's manifesto commitment to building a third runway at Heathrow sticks out like a sore thumb. Opposition from the Tories, the Lib Dems, 28 Labour backbenchers, the high court, environmental groups and local residents in west London means the runway will never be built. It's just a shame that the Labour leadership couldn't join in.

But at least Labour's pledge to block other new runways shows that they're now quietly ditching their own aviation policy. Perhaps they've finally realised that unrestrained airport expansion is not compatible with reducing our emissions and improving local people's quality of life.

Elsewhere in the Labour manifesto, there was a real recognition of the role that low carbon industry can play in Britain's economic recovery. The government would need to back these promises with massive investment in new infrastructure, and energy efficiency in our buildings. Potentially this could bring thousands of new jobs to this country, help to tackle energy security and climate change, and make our homes warm.

David Cameron put the environment at the centre of his push to transform the Conservative Party. By ruling out a third runway at Heathrow and committing to new standards for coal plants that would limit their emissions, he's addressing two of the biggest climate change challenges we face.

But although the Tory manifesto looks good on the headline issues, it doesn't mention that the market needs a jump-start from government to deliver the necessary environmental changes. If Cameron wins he'll have to be bold and face down those who would cut green investment or limit the role central government will have to play in transforming our energy and transport infrastructure.

The Liberal Democrats have the most progressive environmental policies of all the major parties. And they now have a real chance to make them count. As part of a coalition government, they could ensure a focus on developing clean technologies and a new manufacturing base in Britain.

And while Labour and the Tories maintain an inexplicable silence over the massive expense of Trident, the Liberal Democrats have been bold enough to speak up. They recognise that this cold war relic is a massive drain on our resources, and that the upcoming strategic defence review will be meaningless without proper discussion of a £97bn white elephant that even the military doesn't want. On civil liberties they talk about restoring "the right to protest by reforming the Public Order Act to safeguard non-violent protest even if it offends; and restrict the scope of injunctions issued by vested interests."

It has been easy for the Lib Dems to be "holier than thou" as a minority party in permanent opposition. Maybe that is about to change.

John Sauven is UK Executive Director of Greenpeace

Read the manifesto promises on the environment here.