Tony Blair today energetically backed the deals that he and the G8 leaders have struck on tackling climate change and poverty in Africa, claiming that they were "big progress".

Environmentalists and anti-poverty campaigners have already begun to condemn the summit as a failure, claiming that the British Prime Minister has failed to live up to expectations he had created.

Peter Hardstaff, the head of policy at the World Development Movement, said: "The final communique is an insult to the hundreds of thousands of campaigners who listened in good faith to the world leaders' claim that they were willing to seriously address poverty in Africa." George

Gelber, the head of policy at Cafod, the Catholic Agency for Overseas Development, agreed: "The G8's promise to provide the resources to halve extreme poverty by 2015 has not been kept."

There was little comfort from the WWF environmental charity, whose director of climate change, Jennifer Morgan, said: "The Prime Minister must now change his strategy on climate change. While he nobly tried to get President Bush to change, he unfortunately failed."

In in his end of summit press conference, a stung Mr Blair came out of his corner fighting.

Accused that the doubling of global aid to $50 billion was a statistical illusion, the Prime Minister retorted: "I don't think you will find that that's the view of most anti-poverty campaigners.

"People always say that it is never enough, but you find that these things are always said by the people who are not actually getting their hands dirty trying to make things better."

Dismissing what he called the counsel of perfectionism, Mr Blair said that he was a rationalist in politics. "Politics is about getting things done, step by step, making progress. This is big progress and we should be proud of it.

"If anyone had suggested four months ago that we would get the levels of commitment on aid that have been promised in the last few days, no-one would have believed it. On any basis this is a huge uplift in aid. Let's celebrate that and go out and make the most of it."

Today's announcements are the culmination of months of preparation and negotiations to cancel debt, raise levels of aid and ease trade restrictions for the world's poorest countries.

Leaders from Algeria, Ethiopia, Ghana, Nigeria, Senegal, South Africa, Tanzania, and heads of the African Union Commission, IMF, UN and World Bank arrived at Gleneagles this morning to take part in the discussions. At 1300 BST they attended a joint photo call, where the G8 leaders ceremonially signed their communique on what had been decided - believed to be the first time this has ever happened. Mr Blair later jokingly refuted an accusation that this was because he didn't trust them to keep their promises without a signature.

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