One in five people in the world live in poverty

"The long-standing UN target, that every developed country should pledge to give 0.7% of its wealth (its gross national product) in development aid, still remains an aspiration," he said.

"Rio agreed that all countries should reach that target when they could. What we're suggesting is that Johannesburg should agree an actual date for everyone to give 0.7%, though we haven't said what that date should be.

"With more than a billion people - almost one person in five alive today - living in abject poverty on the equivalent of less than one US dollar a day, fixing a date to reach the target at Rio+10 would be a huge step forward."

Global inequalities

Mr Desai said the conference would also concentrate on globalisation, recognising its impact and, he hoped, emerging with something that was seen to address people's concerns about it effectively.

"We must understand there is anxiety out there", he said. "And it's no use telling people their anxieties are misplaced. We have to address the underlying causes that are making them anxious.

"And are the worries really misplaced? Are we certain that globalisation will reduce global inequalities?

"There is a real job to be done in managing globalisation, and the UN has a unique capacity to be that manager and to address people's worries.

"Basically, what the UN does is to amplify the voices of the world's smaller, weaker countries, and of ordinary people everywhere.

"That's what these major conferences like Johannesburg are about. They're not talking shops - they're listening to the world."

Clean drinking water is an essential aid objective

For all that, Mr Desai recognises that parts of the present UN system are unwieldy and often unworkable.

"There's a feeling that there's a proliferation of environmental processes, for example," he said.

"Ozone, climate change, biodiversity, the spread of deserts, persistent chemicals - you name them, they've all got their separate conferences, their separate reporting processes.

"The reporting itself is a burden for governments, let alone the constant travelling to the conferences. I wonder whether we are exploiting the synergies enough, the chances for bringing things together."

Health and hygiene

Several delegates at this conference agree with him: the New Zealand environment minister spent 34 hours travelling to Nairobi, and will take as long to get home again.

Her UK counterpart, Michael Meacher, wants the UN to cut the number of meetings he and his colleagues have to attend. And he says Rio+10 will have to produce practical results.

"The emphasis should be on poverty and development," he said. "We should concentrate on health and hygiene - water supplies and air pollution, which is probably the biggest killer of women and children in developing countries because they cook on stoves which use wood and other biomass fuel.

"We shouldn't get involved in the generalities, which are well documented already. We need specific action plans, at a regional or even country level, looking at specific needs. And I'd like to see an annual report back, so we could identify gaps in provision, and then make resources available to meet them. Then Johannesburg would be a success."