The Government today announced it had accepted the advice of its climate advisers for "ambitious" cuts in emissions in the 2020s.
But while Energy Secretary Chris Huhne said he was adopting the recommendation by the Committee on Climate Change for the fourth "carbon budget", which governs emissions limits between 2023-2027, he said the decision would be reviewed in 2014.
The announcement is a victory for Mr Huhne after a rift in Cabinet in which some ministers opposed the proposals, which will commit the UK to reducing emissions by 50% on 1990 levels by 2025, on the grounds they could damage growth.
Mr Huhne, who faces allegations he asked his estranged wife to accept speeding penalty points on his behalf, had been due to make the announcement in a written statement but was criticised for the move by Labour.
Instead he made an oral statement on the long-term emissions plans to MPs in the Commons.
As reports of the split over the issue in Cabinet emerged last week, environmental groups issued a warning to Prime Minister David Cameron that he risked seriously undermining his pledge to lead the "greenest government ever" if he did not back the targets.
Today Mr Cameron said: "When the coalition came together last year, we said we wanted this to be the greenest government ever.
"This is the right approach for Britain if we are to combat climate change, secure our energy supplies for the long-term and seize the economic opportunities that green industries hold.
"In the past 12 months, we have pursued an ambitious green agenda and today, we are announcing the next, historic step.
"By making this commitment, we will position the UK as a leading player in the global low-carbon economy, creating significant new industries and jobs."
Mr Huhne said the announcement sent a clear signal that the Government was serious about driving the transformation to a low carbon economy in the UK.
He said the Government would continue to press for higher EU targets for 2020 and ambitious action in the following decade.
European climate negotiations would be reviewed in early 2014 and if the UK's trajectory does not match that of Europe, the budget could be revised as appropriate, the Department of Energy and Climate Change said.
Prime Minister David Cameron told the Commons Liaison Committee: "Britain is now leading the world in setting out how we are going to get to a 50% reduction in emissions over the years ahead."
Asked about reports that he had personally had to step in and overrule objections from Business Secretary Vince Cable to the new regime, Mr Cameron said that the agreement on the climate change budget was reached between Mr Cable, Mr Huhne and Chancellor George Osborne at the Cabinet's economic affairs committee.
But he added: "Number 10 is always involved. In this case, my office was involved in trying to encourage a solution.
"Obviously we want to meet the 50% target, and we are doing that.
"The Business Secretary and others had very legitimate concerns about energy intensive industries and how we should try to put together a package to help them, because they are being affected, not just by the carbon budget but by also changes to the electricity market and other costs.
"It doesn't actually help climate change if you simply drive an energy intensive industry to locate in Poland rather than Britain. That was one sticking point. We have a good agreement that is going to deal with that."
And he added: "While we believe that Europe should follow our lead and go for a 30% reduction, they haven't yet committed to that, so there is a review clause in what is being announced in 2014, to make sure that if they are not on that pathway, then we shouldn't put ourselves on it too. But we are confident that we can persuade them that 30% is right."
Mr Cameron added: "I think you will see it is a very good and green announcement about our future intentions, but the Government is quite rightly making sure we are addressing the concerns people have."
The decision to agree to the targets set out by the Committee on Climate Change, as part of a long term effort to meet legally binding emissions cuts of 80% by 2050, was broadly welcomed by environmental campaigners.
Friends of the Earth's executive director Andy Atkins said: "David Cameron's welcome decision to back Chris Huhne over the climate committee's call for tougher global warming action will boost his flagging green credentials."
But he warned: "The inclusion of a get-out clause', in case Europe doesn't cut emissions fast enough, creates needless uncertainty that could dent business confidence - and all just to save face for the Chancellor and Business Secretary, who opposed this agreement.
"The Cabinet row over carbon budgets is a clear warning that some key Government departments are still only thinking about the short-term and would scupper moves to develop a low-carbon economy.
"Ministers must now get on with the urgent task of fast-tracking the development of a low-carbon economy which will create new jobs and business opportunities and wean the nation off its costly addiction to fossil fuels."
John Sauven, executive director of Greenpeace, said the Prime Minister deserved credit for putting a stop to attempts by the Treasury and Mr Cable to "derail the UK's opportunity to be a leader in green growth".
"This announcement makes the creation of new jobs and factories in clean energy industries here more likely and puts the UK back in the race to compete with China, Germany and Silicon Valley in the clean technologies which will power our economies into the future."
He called on ministers to back up the move by giving the new green investment bank the ability to borrow money from day one to give it the power to unlock investment in low carbon technology.
But manufacturers' organisation EEF chief executive, Terry Scuoler, said the decision was bad for manufacturing and the government must quickly address concerns that it would reduce UK competitiveness, as well the fears of energy-intensive industries.
"Government must reassure industry that if there is no European agreement to move to tougher targets by 2014 it will automatically reverse the UK position.
As part of today's announcement, Mr Huhne said that before the end of the year a package of measures would be announced which aimed to reduce the impact on the cost of electricity for energy-intensive industries.
Adam Scorer, director of external affairs at Consumer Focus, said the Government must balance dramatic carbon reduction with the impact the multi-billion pound price tag would have on consumers as well as industry.
He called for greater transparency on bills and said the consequences of higher energy prices would hit the poorest households hardest.
"Many thousands of those struggling to make ends meet may be pushed into fuel poverty.
"The Government must make sure adequate safety nets are put in place to make sure the poorest households get the help they need."
David Kennedy, chief executive of the Committee on Climate Change, which was set up to advise the Government on meeting its legally-binding targets to cut emissions under the Climate Change Act, said he was "delighted" the recommendations had been accepted.
The move is a world-first, with no other country yet setting legally-binding commitments to ambitious reductions in the 2020s, he said.
"Setting and meeting the carbon budget will place the UK in a strong position, both in terms of meeting the 2050 target, and building an economy very well placed to prosper in a low-carbon world.
"The carbon budget will underpin much of the high level ambition set out in the coalition agreement.
"It is important now to translate this ambition into detailed policies with strong incentives."
He said key areas to focus on included reform of the electricity market, developing electric car use and making homes more energy efficient - and said that with the right policies in place, deep cuts in greenhouse gases could be made over the next two decades in power generation, buildings and surface transport at low cost.