Clare Short has criticised the environment minister for diverting attention away from the real issues of the forthcoming Johannesburg Earth summit.

Her comments came after Michael Meacher told the Sunday Times that the government had failed to take the tough decisions needed to protect the environment in policy areas such as transport and housing.

The row came as Number 10 was hit by criticism from environment campaigners over the composition of the UK's delegation to the Earth summit.

The Observer reported that top company bosses would form part of Britain's official delegation - even though in some cases their companies had been accused of polluting the environment.

The delegation includes Bill Alexander, chief of Thames Water which has been repeatedly prosecuted for pollution incidents, and Sir Robert Wilson of mining company Rio-Tinto, which is in the middle of a high profile row over uranium mining in Australia.

Both companies said they were working to improve the environment, but Friends of the Earth condemned the prime minister for being "determined to cosy up to big business at whatever cost".

It is the second time in a week that Number 10's handling of the delegation to Johannesburg has come under fire.

But the international development secretary said the summit was about tackling Third World poverty rather than environmental issues.

Short criticised suggestions that the summit was only about "how we tidy up our environment in the rich countries".

Following Meacher's criticisms, Short told BBC Radio 4's the World this Weekend programme that his concerns had little to do with the summit.

"This isn't an environmental summit. It's a summit about sustainable development,'' she said.

"The biggest challenge to the world is to guarantee to the poor of the world development in a planet that we keep sustainable. It isn't just about how we tidy up our environment in the rich countries."

Questioned on Meacher's comments, she added: "The summit isn't about Britain's transport policy. It is about the sustainable management of the whole world's resources.

"To focus it all on such issues in the UK is not to talk about what the main issues of the summit will be."

After Number 10's attempts to exclude Meacher from the British delegation to South Africa, Short said she had volunteered to stay in the UK but "it was the view of most of my fellow ministers that I needed to be there because the developing countries will be in the lead in this summit".

And she defended the inclusion of business leaders in the delegation, despite some of them having what she described as a "very bad history".

"Calling for business not to be there is very foolish. It is really ostrich, head-in-the-sand. Business practices have to change if we are going to have a sustainable planet," she said.