The UK is not on track to meet targets to cut greenhouse gas emissions through the 2020s, say the Government's climate advisers.
The Committee on Climate Change say some progress has been made in putting in place measures to meet the targets, with record levels of new wind farms, improvements in the fuel efficiency of cars, reducing methane from waste, insulating lofts and replacing boilers in homes.
But other measures saw limited advances in 2012 and progress in some areas risked slowing down in the face of new policies, particularly for renewables and insulation for homes.
More action is needed before the next general election to strengthen policies and increase the rate of emissions cuts, the latest annual progress report to Parliament from the committee urged.
The Committee on Climate Change's chief executive David Kennedy said: "Although the first carbon budget has been comfortably achieved and the second is likely to be achieved, this is largely due to the impact of the economic downturn.
"There remains a very significant challenge delivering the 3 per cent annual emissions reduction required to meet the third and fourth carbon budgets, particularly as the economy returns to growth.
"Government action is required over the next two years to develop and implement new policies. A failure to do this would raise the costs and risks associated with moving to a low-carbon economy."
Last year emissions rose by 3.5 per cent, mostly due to the cold winter and more use of coal instead of gas to make electricity, with the dirtier fossil fuel rising from 30 per cent of the energy mix in 2011 to 39 per cent in 2012, the report said.
Without these effects, emissions would have fallen by around 1 per cent to 1.5 per cent, short of the 3 per cent annual reductions which will be needed to meet targets to cut greenhouse gases in the 2020s.
The UK comfortably met its first five-year "carbon budget" to reduce emissions up to 2012, and is on track to meet the next set of goals up to 2017, but this is largely the result of the recession rather than the impact of climate policies.
It is a "very significant challenge" to increase the pace of reductions to meet the third and fourth carbon budgets up to 2022 and 2027, especially when the economy returns to higher levels of growth which could spark more emissions.
The report recommended a range of measures across the economy from making eco-driving part of the driving test to tightening building regulations to ensure homes are "zero-carbon" from 2016.
The Government should look at measures to cut emissions from waste, such as banning biodegradable rubbish from landfill or bringing in more separate food leftovers collections, and push to reduce gases that come from air-conditioning and refrigeration.
The expert advisory panel repeated its call for the Government to set a target to slash emissions from the power sector by 2030, as was proposed by MPs earlier this month, to give investors confidence to invest in low-carbon energy such as renewables and nuclear.
The annual report warned that last year there were very low levels of solid wall insulation installed, take up of low-carbon heat pumps and improvements in energy efficiency in commercial buildings and industry.
And there is a high risk that new policies will not deliver what is needed, including the Government's flagship energy efficiency policy, the green deal, which meets the upfront costs of home energy improvements with the money paid back through savings on bills.
The committee warned that incentives for insulation under the green deal were weaker than the system it was replacing, and may need to be strengthened.
And plans for delivering billions of pounds of investment in low-carbon power under reforms of the electricity market must give more clarity and more confidence on the Government's support for green energy.
The warning came just hours after US President Barack Obama said he would redouble efforts to engage international partners in reaching a new global agreement to reduce carbon pollution through concrete action.
Speaking at Georgetown University in Washington yesterday the President tried to revive his stalled climate change agenda, promising new rules to cut carbon emissions from US power plants and other domestic actions including support for renewable energy.
He also signalled he would block construction of the Keystone XL oil pipeline from Canada if it contributed to climate change, though that does not mean the project is doomed as a State Department report, which Obama could reference, has said the pipeline would not change the outlook for carbon emissions because the development of Canada's oil sands would continue whether it is approved or not.
With Congress unlikely to pass climate legislation, Obama said his administration would set rules using its executive authority.
"We limit the amount of toxic chemicals like mercury and sulfur and arsenic in our air or our water, but power plants can still dump unlimited amounts of carbon pollution into the air for free," Obama said.
"That's not right. That's not safe. And it needs to stop."
Obama's first-term attempt to reduce climate-warming carbon emissions in a "cap and trade" system was thwarted by Congress, and his administration's long process of studying whether to approve the Keystone XL pipeline has raised hackles from business groups and Republican critics.
Obama said he had directed the Environmental Protection Agency to craft new emissions rules for thousands of power plants, the bulk of which burn coal and which account for roughly one-third of US greenhouse gas emissions.
He said the US had doubled electricity generated from wind and solar power during the past four years but it must double that figure again and pledged the federal government would consume 20 per cent of its electricity from renewable sources within the next seven years.
Speaking at Georgetown University in Washington, the President also urged other countries to back his call for an end to public financing for new coal plants overseas, unless they deploy carbon-capture technologies or there was no other viable way for the poorest countries to generate electricity.