As countries responsible for more than 80% of the world's emissions inscribe their commitments to the Copenhagen Accord, the Prime Minister labelled the step a "turning point" in leading to a peak in emissions by 2020 and the target of keeping temperature rises below 2C.

But he called for more action and said lessons must be learned from the "flawed" process at the Copenhagen conference on climate change in December. The two weeks of talks in the Danish capital descended into chaos with repeated clashes between rich and poor countries and wrangling over procedures.

The Copenhagen Accord, agreed on the last day, got developing countries to commit to action on their emissions, laid out finance to help developing countries, recognised temperatures should not go above 2C, and ensured nations would monitor action to curb greenhouse gases. But the deal - agreed by 49 countries - had no timetable for securing a legally-binding international treaty and there were no targets for global greenhouse gas cuts.

Countries were expected to submit pledges for reducing emissions by Sunday, although it is understood commitments will continue to be inscribed over the coming days.

In a letter to Dr Alan Williams, chair of the House of Commons Liaison Committee, Mr Brown - who is due to appear before the panel of senior MPs on Tuesday - said: "Over the next few weeks the initial phase of the Copenhagen Accord will be completed.

"If those countries which agreed the Accord in Copenhagen inscribe into it the commitments they made in the run-up to the conference - and I believe it is very much in the global interest that they should do so - the international community will have taken the first steps towards a historic transformation in the trajectory of global emissions.

"For the first time, the world will see, collected together, strong mitigation commitments by countries representing more than 80% of global emissions.

"If those commitments are then implemented to their maximum potential, they could lead to emissions peaking by around 2020 or before, representing the crucial first step towards the level of reductions required to hold global temperature increases to under two degrees.

"We will still have to do more - and we must review this in 2015 as the Accord states. But these commitments will nevertheless represent a turning point in the global battle to combat climate change."