Efforts to secure a legally-binding climate change deal failed last week because talks were "held to ransom" by a small number of countries, Gordon Brown said today.
As the UK pointed the finger of blame at China for blocking progress at the UN-sponsored summit in Copenhagen, he called for a new international body to take charge of future negotiations.
Days of chaotic talks between more than 190 countries produced an accord that average world temperature rises should not exceed 2C but without commitments to emissions cuts to achieve it.
There was also agreement on a fund, to reach 100 billion US dollars by 2020, to help poorer countries deal with global warming, but no precise detail on where the money will come from.
The Prime Minister, who spent four days in the Danish capital trying to secure a stronger deal, admitted that he feared the talks could collapse without even those advances.
And, in a webcast to be posted on the Number 10 site, he pledged to continue pressing for a binding deal and demanded action to ensure a minority of countries could not block future efforts.
"The talks in Copenhagen were not easy. and, as they reached conclusion, I did fear the process would collapse and we would have no deal at all," he said.
"Yet, through strength of common purpose, we were able finally to break the deadlock and - in a breakthrough never seen on this scale before - secure agreement from the international community."
Calling on the world to "learn lessons" from last week's frantic scenes, he said: "Never again should we face the deadlock that threatened to pull down those talks; never again should we let a global deal to move towards a greener future be held to ransom by only a handful of countries.
"One of the frustrations for me was the lack of a global body with the sole responsibility for environmental stewardship.
"I believe that in 2010 we will need to look at reforming our international institutions to meet the common challenges we face as a global community."
Climate Change Secretary Ed Miliband earlier accused China of "hijacking" the Copenhagen summit and said Beijing had "vetoed" moves to give legal force to the accord and prevented agreement on 50% global reductions in greenhouse emissions - 80% in the most developed countries - by 2050.
"We did not get an agreement on 50% reductions in global emissions by 2050 or on 80% reductions by developed countries. Both were vetoed by China, despite the support of a coalition of developed and the vast majority of developing countries," he wrote in The Guardian.
"Together we will make clear to those countries holding out against a binding legal treaty that we will not allow them to block global progress," he said.
"The last two weeks at times have presented a farcical picture to the public. We cannot again allow negotiations on real points of substance to be hijacked in this way.
"We will need to have major reform of the UN body overseeing the negotiations and of the way the negotiations are conducted."
Despite his frustrations, Mr Miliband insisted that Britain was right to sign the limited Copenhagen accord, which he said delivered "real outcomes" on temperature rises and finance.
"We should take heart from the achievements and step up our efforts," he said.
"The road from Copenhagen will have as many obstacles as the road to it. But this year has proved what can be done, as well as the scale of the challenge we face."
Oxfam joined the calls for a revamp of the negotiating system to avoid a repeat of what its "global ambassador" Archbishop Desmond Tutu called the "profoundly distressing" failure of the Copenhagen talks to get a binding deal.
The aid charity warned that by the time of the next scheduled round of UN-sponsored talks, in Mexico in December, around 150,000 people would have died and a million been displaced as a result of climate change.
It said a series of ministerial-level meetings should be held before then and the talks given a permanent base - as Geneva serves as a location for world trade talks - and more help given to developing countries.
Oxfam's climate change adviser Antonio Hill said: "The Copenhagen Accord is hugely disappointing but it also reveals how the traditional approach to international negotiations, based on brinkmanship and national self-interest, is both unfit for pursuing our common destiny and downright dangerous.
"There is too much at stake for this politics-as-usual approach. We must act quickly to address the shortfalls of these negotiations so that we can make up for lost time and tackle climate change with the decisiveness and urgency needed. This cannot happen again."
Archbishop Tutu said: "The failure of the political process in Copenhagen to achieve a fair, adequate and binding deal on climate change is profoundly distressing.
"A higher purpose was at stake but our political leaders have proven themselves unable to rise to the challenge. We must look to the future. Our leaders must regroup, learn and make good their failure for the sake of humanity's failure."
Speaking via videolink to a gathering in London, Mr Brown said reform of the UN decision-making was necessary because the final Copenhagen accord had not represented the level of agreement across the world.
The Prime Minister said: "We have just got to find a way to actually move the process forward, because what Copenhagen disguised in its last day was that the level of agreement between the countries was a great deal higher than was being reflected in the detailed text that was being provided," the Prime Minister said.
He pledged to work with island states, the African Union and directly-affected countries like Bangladesh among others to develop a "better process where the agreement that we have amongst each other is better reflected in the text".
Mr Brown also called on the United States and China to show more "ambition", arguing that it was not enough for the EU to say it was prepared to cut emissions by 30%.
"What we need is not just one part of the world going to higher ranges of ambitions, we need the other parts of the world as well," Mr Brown said.
"If America and China were able to show that they were doing more, and I believe that they could, then all countries - Australia, Brazil, Japan, Korea - all these countries that have got ranges would be prepared to go to their highest level of ambition."
Describing the decision-making process in the Danish capital as "at best flawed, at worst chaotic", Mr Brown said: "The United Nations needs to be in a position where we can get agreements with Governments working together without having these last-minute negotiations where threats and fear can actually dominate the proceedings."
The Prime Minister said he remained committed to achieving a legally-binding deal and would continue to work to achieve it.
He added: "I believe there is sufficient goodwill around the world to want to make this happen, and I can assure you that over the next weeks and months we will press hard not only for a climate treaty but for the means in which the world can come together."
Tory leader David Cameron described the summit as disappointing.
He said: "We should be thankful for the small things that have been achieved like the 2C limit on temperature rises and the good work on rainforests.
"But it's disappointing overall because there are no carbon reduction targets, the details on help for poorer countries to tackle global warming is vague and it's not a legally binding treaty.
"We need now to step up the work to get that done."
Lessons should be learnt from Copenhagen about how to make the machinery of international talks work better, he added.
"I think we need better and different and more rigorous machinery to get countries together and to get the preliminary work done first," he said. "We need to get the Sherpas to do more before they get to the summit."
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