A new report has laid bare the UK's pretensions to have cut greenhouse gas emissions over recent years.
Ministers have claimed global leadership in reducing CO2 emissions and urged other nations to follow suit.
But the official Climate Change Committee (CCC) said that the UK's total contribution towards heating the climate has actually increased.
This is because the UK is importing goods that produce CO2 in other countries.
The UK has been cutting emissions at home, but it has been importing more goods from other countries, pushing up CO2 emissions there.
The UK is second highest importer in the world of these so-called "embodied" emissions.
Each individual in the UK is responsible for double the imported emissions of someone in Germany, which has kept its manufacturing base.
BBC News has been highlighting this issue for some time and MPs asked the committee to examine it last year.
Total emissions target?
The committee said although production of CO2 is down 20% in the past two decades, the overall trend is up 10% because the cuts in production emissions have been outweighed by CO2 in the form of imported goods.
Some commentators have argued that the UK should switch to declaring its total emissions, instead of its production emissions.
The committee rejected this option as it is hard to quantify imported emissions and difficult to influence other nations' climate policies.
The CCC's chief executive, David Kennedy, told the BBC that it would be a mistake to target imported emissions in official analysis.
"High levels of imported emissions reflect the need for emissions reductions in other countries if climate objectives are to be achieved," he said.
"We should focus on reducing emissions produced in the UK, and proactively supporting an international agreement to reduce global emissions, following which our imported emissions would fall."
Mr Kennedy said border tariffs on CO2 embodied in imported goods should not be ruled out as an interim measure while the world struggles towards a global agreement.
The report did contain some good news on climate policy for the government.
Some lobbyists have argued that UK's unilateral climate targets are forcing up energy prices and driving manufacturing jobs abroad, but the committee found this false.
Impact on jobs 'negligible'
It said the UK exported its manufacturing jobs during the structural changes of the 1980s (during the Thatcher government) and pointed out that few industrial jobs are being lost at present.
It said the impact of carbon policies on jobs is "negligible", although it did not offer a figure.
The committee also said that energy costs due to low-carbon policies are expected to rise by 20-25% from 2011 to 2020 for industrial users.
But it said that across industry as a whole, energy costs account for around 3% of total costs, so increasing energy prices are unlikely to have much impact.
It admitted that the government may need to continue support for firms needing large amounts of power.
The energy-intensive industries account for around 2% of UK GDP and 2% of jobs.
The committee agreed that if nations fail to agree a meaningful deal on CO2, the UK should reconsider in 2020 its own unilateral climate change targets.
Gareth Stace from the manufacturers' association EEF said: "This report (shows) unilateral climate change policies are adding costs that are not borne by our competitors. The government must ensure that cost effectiveness is at the heart of its approach to securing investment in new low carbon energy."
But the green group WWF said the report showed the German government had over-compensated its industry and urged the UK government not to follow suit.
Friends of the Earth's Shrubsole said: "Ministers must come clean about our carbon emissions - it's no good pretending they're falling, when UK imports have actually caused them to rise. This reveals the truth behind attempts to blame countries like China for climate change, when a significant proportion of their emissions are produced in order to maintain our quality of life."
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