A Commons committee has criticised the government's "incoherent" plans to tackle global warming.
MPs on the environmental audit committee said ministers were failing to keep up with the latest scientific evidence.
The draft Climate Change Bill includes a legally binding target for the UK to cut carbon emissions by 60 per cent by 2050.
But, said the committee, this was now "very unlikely" to be enough to meet the government's ambition of stabilising the rise in global temperatures at 2C.
"The government's policy towards the UK's 2050 target is clearly incoherent," the report said.
"This target should be strengthened to reflect current scientific understanding of the emission cuts required for a strong probability at stabilising warming at 2C."
Responding to the findings, environment secretary Hilary Benn said: "The UK should be proud of its record on tackling climate change.
"We are on track to meet and go beyond our Kyoto target. Government must rightly lead in combating climate change and is helping individuals and businesses to play their part, but also working to secure a strong and comprehensive global deal to reduce emissions.
"But we recognise that to reach our long term goals we need to do more. That's why we will put in place ambitious climate change legislation, the first of its kind in the world, which will help us cut emissions at home, and show we're willing to make our contribution as part of a global agreement."
But committee chairman Tim Yeo said that carbon reduction measures "have not delivered as much as predicted and forecasts of future emissions have consistently drifted upwards".
