Mr de Boer is known to be disappointed with the outcome of the last summit in Copenhagen, which drew 120 world leaders but failed to reach more than a vague promise by several countries to limit carbon emissions. However, he denied that his decision to quit was a result of Copenhagen.

Mr de Boer will become a consultant on climate and sustainability issues for global accounting firm KPMG and will be associated with several universities.

“Copenhagen did not provide us with a clear agreement in legal terms, but the political commitment and sense of direction to a low-emissions world are overwhelming,” he said. “This calls for new partnerships with the business sector and I now have the chance to help make this happen.”

In recent weeks he came under pressure to sack embattled UN climate change scientist Rajendra Pachauri over his handling of an exaggerated claim about glacial warming in UN’s Intergovernmental Panel on Climate Change report in 2007.

Mr de Boer had maintained the credibility of the IPCC, which Mr Pachauri chairs, remained intact despite its admission it had erred by predicting Himalayan glaciers could disappear by 2035 if global warming was not checked.

Mr de Boer said last night he believed global talks “are on track”, although it was uncertain that a full treaty could be finalised at the next summit in November.

The partial agreement reached in Copenhagen, brokered by Barack Obama, “was very significant”, he said. But he acknowledged frustration that the deal was merely “noted” rather than adopted by all countries.

The media-savvy former Dutch civil servant was credited with raising the profile of climate issues through his press encounters and his lobbying of world leaders.

But his travel and frenetic diplomacy failed to bridge the suspicions and distrust between developing and industrial countries that blocked a final agreement at Copenhagen in December.

People who know him say he was more disheartened by the snail-paced negotiations than he was ready to admit.

Mr de Boer, 55, was appointed in 2006 to shepherd an agreement to succeed the 1997 Kyoto Protocol, which required industrial countries to cut greenhouse gas emissions an average 5 per cent. He said the high point of his efforts was the agreement by developing countries, reached at the 2007 conference in Bali, to join efforts to contain global warming in return for financial and technical help from the wealthy nations.

The Bali meeting was so intense that during its final meeting, when he was accused of mishandling the arrangements, Mr de Boer left in tears. He returned to an ovation.

AP