Gordon Brown spent four days in the Danish capital trying to secure a stronger deal (Telegraph photo )
Days of chaotic talks between more than 190 countries produced an accord that average world temperature rises should not exceed 2 degrees Celsius but without commitments to emission 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.''
Ed Miliband, the Environment Secretary, 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 per cent global reductions in greenhouse emissions - 80% in the most developed countries - by 2050.
''We did not get an agreement on 50 per cent reductions in global emissions by 2050 or on 80 per cent 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 (London) 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.