A world treaty on climate change will be delayed by up to a year and is likely to be watered down because countries with the highest greenhouse gas emissions are refusing to commit to legally binding reductions.

British officials preparing for next month’s UN summit in Copenhagen said the best that could be hoped for was that national leaders would make “political agreements” on emission cuts and payments to help poor countries to adapt to climate change. These agreements would be non-binding, however, and could later be revised or rescinded by national parliaments.

At pre-summit talks in Barcelona, the officials said the final agreement would not emerge until at least six months after the Copenhagen summit, which ends on December 17. They said they hoped another meeting would be convened by next December to allow leaders to sign the treaty.

The admission that no treaty will be signed at Copenhagen marks the failure of the process agreed at a UN meeting in Bali in December 2007, when industrialised countries agreed to deliver a binding climate-change agreement within two years. The delay has angered developing countries, which say they are already suffering from man-made climate change.

The Global Humanitarian Forum, based in Geneva, has estimated that more than 300,000 people are killed each year by climate change, nearly all of them in poor countries.

Delegates from 190 countries are now trying to agree a new timetable for signing a treaty but it is likely to be vague and contain no clear deadline.

Ed Miliband, the Energy and Climate Change Secretary, told the House of Commons yesterday that little progress was being made in Barcelona, where delegates are discussing more than the 1,000 remaining disagreements over wording. He said: “The UN negotiations are moving too slowly and not going well. We would have preferred a full legal treaty, it has to be said. I think the important thing about the agreement we now seek in December is that while it may be a political agreement it must lead, on a very clear timetable, to a legally binding treaty.”

Artur Runge-Metzger, the European Commission’s negotiator on climate change, said in Barcelona that the absence of commitment from the United States on emission cuts was a key factor contributing to the delay, although other countries were also to blame. He said that without a treaty the EU would agree to cut its 1990 emissions by only 20 per cent by 2020, whereas with a treaty it would agree to a 30 per cent cut. Cuts of 25-40 per cent are needed by developed countries if a dangerous rise in global temperatures is to be avoided, according to the Intergovernmental Panel on Climate Change, a UN-appointed group of more than 2,000 scientists.

China, the world’s largest emitter of greenhouse gases, has also failed to announce targets. It has promised to cut carbon dioxide emisissions per unit of GDP but has not said by how much.

Benedict Dempsey, Save the Children’s humanitarian policy officer, said: “The cost of any delay to a climate deal will be counted in children’s lives. Save the Children estimates that 250,000 children could be killed by climate change next year.

“Negotiators must realise that the world’s poorest communities can’t afford to wait.”

Joss Garman, of Greenpeace UK, said the EU should put more pressure on the US to agree targets. Copenhagen was the best chance to slash emissions, he said, but added “politicians seem determined to blow it”.

He said that the US, influenced by “Big Carbon special interests”, was “a dead weight” on the talks.

Times recommends

• Energy-saving ideas from switched-on professor
• Rooks are as clever with tools as chimpanzees
• Burping of the lambs blows roast off menu