The Committee on Climate Change highlighted failures in policies such as improving the energy efficiency of homes, where the instalment of insulation has plummeted since new schemes were introduced last year.
Under current rates of progress, the country is set to cut its emissions by around 21% to 23% between 2013 and 2025, well short of the 31% set out in the "carbon budgets" for managing greenhouse gas reductions, a report from the committee said.
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Committee chairman Lord Deben warned the UK was not on track to meet its legally-binding target to cut greenhouse gases by 80% by 2050, and the longer the country left tackling its emissions, the more expensive it would become.
Lord Deben said: "Climate change demands urgent action.
"We have started on the road and we are being joined by much of the rest of the world.
"However, despite our success, the UK is still not on track to meet our statutory commitment to cut emissions by 80%.
"The longer we leave it, the costlier it becomes.
"This report shows the best and most cost-effective ways to ensure we meet our targets. There is no time to lose."
In its sixth annual progress report to Parliament, the Committee on Climate Change said the first five-year carbon budget from 2008 to 2012 had been met as a result of policies and the impact of the recession.