David Cameron has moved to resolve a Cabinet row over the UK's climate change targets, with an agreement on emissions to be announced on Tuesday.
This will see drastic cuts in greenhouse gas emissions to 2027 and an overhaul of the way energy is produced.
But ministers worried about the impact on the economy and burdens on industry have secured a get-out clause.
The targets will be reviewed if European nations backslide on their own climate commitments.
The BBC understands the prime minister intervened after leaked letters showed a disagreement between energy and climate change secretary Chris Huhne and Lib Dem colleague, Business Secretary Vince Cable, on whether to accept the recommendations of the Committee on Climate Change on emissions cuts.
The official advisory body has urged the UK to accept a global agreement which roughly equates to an emissions cut of 50% - based on 1990 levels - by 2025.
The settlement - which will form part of the UK's fourth carbon budget - is being categorised as a victory for Mr Huhne but the BBC understands the Treasury, the Department of Business and the Department of Transport refused to sign up to the deal without the get-out clause.
The agreement was due to have been finalised at the Cabinet's Economic Affairs sub-committee on Monday but disagreements were so serious that negotiations were concluded outside the committee.
It is understood that Cabinet Office minister Oliver Letwin played a major role in negotiations while the prime minister personally intervened to broker a final agreement.
Mr Cameron is already under fire over environmental policy with critics saying he has failed to keep his promise to create the greenest government ever. If he had rejected the climate committee's advice, environmentalists claim he would have lost all credibility.
The issue has divided coalition colleagues from within the same party, with Mr Cable understood to have infuriated Lib Dem colleagues by trying to block the 2027 target.
While some companies have been urging government to adopt the target to secure a low-carbon economy in the UK, Mr Cable promoted the position of the elements of the business lobby most likely to be threatened by it.
Meanwhile Foreign Secretary William Hague put the case for strong carbon targets to keep up with countries like China in the move towards low-carbon energy, and to retain the UK's international moral leadership on the issue.
Labour have previously said that if ministers did not accept the committee's recommendations in full it would amount to a "green betrayal" and accused Mr Huhne of failing to "show leadership" over the issue.
They say carbon reduction targets must not be watered down as part of efforts to alleviate red tape on industry.
Greenpeace described the agreement as "rare victory for the green growth agenda" in the face of what it said was "vehement" opposition from the Treasury and the Department of Business.
But Friends of the Earth said Mr Huhne should have gone further and accepted advice to tighten the UK's existing 34% emissions reduction target, by 2020, to compensate for the cuts already achieved due to the recession.
A Department of Energy source defended the government's handling of the issue, arguing that it would be wrong to pre-empt discussions underway in the EU and the UK was still arguing to increase the EU 2020 target from 20% to 30%.