The government's policy on global warming is "incoherent" and will not stem global warming, MPs have warned.
The Commons environmental audit committee said ministers were failing to consider the latest scientific evidence - with the result targets to cut emissions will have little effect on global climate change.
Given this, the government is "very unlikely" to meets its aim of curbing the rise in global temperatures at 2C, MPs warned.
The draft climate change bill proposes a legally binding target to cut emissions by 60 per cent by 2050.
However, the committee warned: "The government's policy towards the UK's 2050 target is clearly incoherent.
"This target should be strengthened to reflect current scientific understanding of the emission cuts required for a strong probability at stabilising warming at 2 degrees C."
The committee called on the government to be "braver" in setting targets, arguing tougher action on climate change must be made politically possible.
Tim Yeo, the committee's chairman said: "Carbon-saving measures have not delivered as much as predicted, and forecasts of future emissions have consistently drifted upwards.
"To make things worse, these forecasts have not been updated often enough, which means that by the time ministers knew the UK's 2010 CO2 target was significantly off-track it was too late to do much about it."
Singled out for criticism was the government's refusal to include emissions from international aviation and shipping in its targets, already highlighted for concern by environmental groups.
The committee said it was "unimpressed" with the government's arguments for excluding aviation emissions, pointing to existing frameworks that could be adapted to monitor emissions.
Environment secretary Hilary Benn insisted the UK could be proud of its record on climate change.
Mr Benn said: "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."
Friends of the Earth (FoE), which has consistently lobbied for a tougher climate change bill, was vindicated by the committee's report.
FoE spokesman Robin Webster said: "This report shows that the government's proposed climate change law is simply not strong enough.
"The law must deliver the emissions reductions which scientists say are needed and it must cover emissions from all sources."
Through the Big Ask campaign, FoE has been campaigning for annual emissions cuts of three per cent a year, including emissions from international shipping and aviation.
Meanwhile, climate change scientists reported today that global warming is to blame for the increasing number and ferocity of hurricanes.
Researches in the US found the average number of Atlantic storms per year has doubled since 1905, blamed on rising sea temperatures.