Gordon Brown has hailed "major progress" at the G8 summit after leaders agreed on a carbon emissions target.

The world's leading industrialised nations agreed to cut emissions by 50 per cent by 2050 at the meeting in Japan.

The group - consisting of Britain, the US, Germany, Japan, France, Italy, Russia and Canada - has also pledged to stick to a 2005 promise to double international aid by 2010.

The Prime Minister said: "There has been major progress on the climate change agenda, beyond what people thought possible a few months ago.

"Countries which previously objected to setting overall targets have accepted these targets subject to there being an international agreement."

The UN' top climate official, Yvo de Boer, said the climate change statement had positive elements but that the lack of mid-term numerical targets was a critical omission.

Mr de Boer, head of the UN Framework Convention on Climate Change, under which the Kyoto pact falls, said: "Looking at the thing as a whole I have mixed feelings on it. On the one hand it contains a number of positive elements.

"It's positive in that it talks about ambitious economy-wide mid-term goals for industrialised countries. It's positive in that it recognises there is a difference between rich and poor nations and what they should be expected to do.

"What I find lacking is any kind of language on where industrialised nations, G8 nations, want their emissions to be in 2020 and I think that is critical to making progress in the negotiations."

Meanwhile, Mr Brown played down controversy over a banquet enjoyed by himself, other leaders and their partners on Monday night shortly after they had been discussing world food shortages.

He said he would "not support any unnecessary expense" on such things but said the meal had not been as lavish as some reports claimed, adding: "The question in the end is whether it yields results."

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