Decisions made at the world summit in South Africa need to be translated into genuine change, according to Prime Minister Tony Blair.

Just hours after his return from the talks at Johannesburg, Mr Blair stressed that "significant progress" had been achieved.

The overall outcome of this Johannesburg summit is truly remarkable

Margaret Beckett Environment Secretary

But he conceded: "It won't have done everything we want."

The prime minister was speaking at a presidential-style news conference in his Sedgefield constituency.

The UN Summit reached a deal to fight poverty without wrecking the environment.

'Criticism overplayed'

But green campaigners complained that there were insufficient tough targets for more use of renewable energy sources, instead of polluting fossil fuels.

Mr Blair told reporters on Tuesday that while the role of summits should not be over-stated, they "should not be dismissed either".

"I think the summit made significant progress ... some of the criticism is overplayed," he said.

"I think that what now needs to happen is that we keep the agenda moving forward and push those decisions through and make sure that ... the things that we determine in principle at the summit are actually translated into genuine change on the ground."

Porritt says the EU has to reflect on a bad failure

Environment Secretary Margaret Beckett hailed the overall outcome of the Johannesburg talks as "truly remarkable".

As the 10-day summit draws to a close, only a dispute over the wording of a clause about reproductive health rights for women is delaying the final action plan.

The European Union is pressing ahead with its own plan to boost the use of renewable energy sources after plans on the issue were watered down.

'Our best shot'

Mrs Beckett said EU ministers had held out until the bitter end for agreement but it became crystal clear they could not overcome resistance from America and some developing countries.

But the environment secretary was upbeat about the success of the talks as a whole.

Mrs Beckett said: "The overall outcome of this Johannesburg summit is truly remarkable.

"We had to give it our best shot - to get the best deal we could - and we did."

Mrs Beckett pointed to targets and action plans agreed on giving people access to sanitation, on toxic chemicals, biodiversity and natural resources.

'Poor outcome'

But attempts by politicians to trumpet the success of the summit did not impress Jonathon Porritt, the government's sustainable development adviser.

He described the compromise reached at the world summit over boosting the use of solar and wind power "a really poor outcome".

Mr Porritt told BBC Radio 4's Today programme the summit agreement was a start "but just about the smallest start that can possibly be made".

"We have a really poor outcome, in particular on renewable energy."

He added: "The EU will need to reflect very carefully on why it failed so badly here, not just to persuade America ... but why the EU failed to persuade developing countries that this was the best way forward."

'Start of a revolution'

Mr Porritt is not in Johannesburg and Mrs Beckett suggested he had been fed "duff" information.

But EU nations had been unable to convince other countries of the wisdom of setting a single global target on renewable energy, she said.

Mrs Beckett told BBC Radio 4's World At One that views of the summit needed to be more balanced.

She added: "If we carry out what's been agreed at this summit it will be a revolution in the lives of the poorest people in the plant and the beginnings of the revolution we need in saving our planet from environmental damage."

Now the European Union has come up with its own plan, offering to establish links between European and developing countries that are interested in setting targets for encouraging renewable energy.