I am delighted that the Liberal Democrats have reaffirmed our commitment to creating a zero carbon Britain by the year 2050.
But we need to be much clearer than the Fresh Start pre-manifesto about how we would achieve it.
With every general election, we set out how much our policies would cost and how we would pay for them.
We should be just as open an honest about how we will cut greenhouse gas emissions.
Our next general election manifesto should set out an alternative carbon budget showing, for every major government department and every major policy area, how we will put the UK on a zero carbon path.
We need to show, with policies and figures, how every major department- for instance, energy and climate change, transport, communities, Treasury – will play its part.
[This a slightly edited version of my intervention in the debate on A Fresh Start for Britain at the Liberal Democrat conference, 22 September 2009]