"Could have done better" is the Wiltshire Wildlife Trust's verdict on the World Summit on Sustainable Development, which finished last Thursday.

The Johannesburg summit, which was attended by all the world's leaders, aimed to bring countries together to look at ways of cutting pollution and improving the lives of people in poorer countries.

But Dr Gary Mantle, director of Wiltshire Wildlife Trust, said it has not gone nearly far enough on crucial environment issues.

He said: "We are encouraged by the commitments made on areas such as energy and water and the way the environment has moved up the political agenda."

But he warned that more needed to be done. "The summit's final declaration includes a pledge to ensure clean access to drinking water.

"It also commits the world to phasing out the use of toxic chemicals.

"We could address several of these issues at once if we paid farmers to produce clean water and halted the subsidies that pollute it."

Every year the UK taxpayer has to spend £30 million cleaning up our water and taking out pesticides and other chemicals.

Dr Mantle said: "The irony of that is that we have already paid for them to be put in, thanks to the unsustainable land management encouraged by the Common Agricultural Policy.

"This madness is a double whammy for the tax payer and a killer punch for wildlife."

Recent studies by the Wildlife Trust, including one on fly life on the River Wylye in South Wiltshire, show marked reductions in flies, birds, flowers and fish in Wiltshire, believed to be caused largely by chemical run-off from farmland into streams and rivers.

Environmental catastrophes like the 2000 floods cost £3 billion to clear up, and the Trust has warned politicians of the vital importance of rivers in acting as natural 'sponges,' soaking up floodwater. Dr Mantle said: "A lot of fine words were spoken in Johannesburg. They will only mean anything if they now lead to action."