With both Brown and Cameron today parading their green fig-leaves, I thought I'd take a look to see what they're hiding.

Cameron - belonging to the party of nuclear power, personal wealth, unfettered consumption and the right-to-drive - seems an unlikely green convert. But, straight off, I have to say that Brown, being responsible for many years of painfully slow progress on climate change, is just as in need of his new fig-leaf.

The role of Cameron's fig-leaf isn't hard to discern. Behind it lies the putrid and hardened reputation of the old Tories, sleazy and all too prone to finding a way of doing something unpleasant to the British voter. The glamour and freshness of green issues chimes well with the voters he wishes to chase - liberal-minded, intelligent, and educated. But for all the talk, the voters are yet to be convinced, I believe.

They have good reason not to be. Today, my colleague Siân Berry, our new London Mayoral candidate, released a report detailing the Top Ten Tory Eco-Cons. These include support for nuclear power, support for new roads, support for aviation growth and full-blown opposition to EU green schemes, where their voting record is among the worst of all UK parties.

In my experience, in London, their opposition to congestion charging also gives a clear indication of real Tory priorities - despite this being one of our most successful measures for reducing traffic congestion and CO2 emissions.

Cameron himself has continued to laud the virtues of cars and traffic growth, saying we can solve the problems with new green technologies. They might help, but we know that, in all seriousness, a true green would tell the public that we need to drive less and build fewer roads.

So, let's turn to Brown, to see if he performs any better, underneath his very new green fig-leaf. For a start, under Brown, we find that carbon emissions have, in fact, risen, rather than fallen, and Labour have built more roads and created huge aviation growth. 

What Brown could be doing is more telling, compared with his rather lacking policies. We might expect that a Labour government would put money into trains, buses and British industry, or into reducing household bills by fitting insulation. That's the sort of thing Labour used to be known for - and now we can see that there are good green reasons for these sort of policies. But Brown has been as bad as the Tories in leaving things to the market.