Tony Blair was ambushed by Zimbabwe's Robert Mugabe and Namibia's president Nujoma at the Johannesburg summit yesterday.

The African leaders, in what appeared to be a co-ordinated protest, slammed the prime minister and Britain with accusations of colonialism.

To loud applause Mugabe said: "Blair, keep your England and let me keep my Zimbabwe."

Blair was out of the conference hall at the time, but sat, stony faced, to hear president Nujoma say: "Here in southern Africa we have one problem and it was created by the British. The honourable Tony Blair is here and they created the situation in Zimbabwe."

In a day of outrage, environmentalists claimed the summit's final agreement has been so watered down that it is almost a step backwards.

America got its way and there will be only a reference to renewable energy increases that are not tied to any timetable.

The delegates did, however, agree to halve the number of people who lack access to proper sanitation by 2015.

Earlier, the prime minister used his speech to repeat his belief that poverty in Africa is a scar on the conscience of the world that must be healed.

He added: "Poverty and environmental degradation, if unchecked, spell catastrophe for the world."