There can be few sensible people who seriously expect anything significant from the Earth Summit in Johannesburg.

All the high-flown rhetoric may be worthy and well meaning but the real beneficiaries will inevitably be the multinational corporations and their steady progress towards globalisation. Poor countries are merely pawns.

And in a hopelessly corrupt continent such as Africa, the Summit host and chairman, Thabo Mbeki, President of South Africa, cuts a rather less than impressive figure bleating on about global apartheid and warning of a society based on "the savage principle of the survival of the fittest".

He and his next-door neighbour, President Mugabe of Zimbabwe, must have worked on that one together.

The whole charade will cost well over £33 million.

However, what will surely be seen in years to come as one of the most blatantly cynical moves in the exploitation of the world's poorer countries, is the United Nations plan to involve the McDonald's burger corporation in a partnership with its international children's fund, UNICEF.

The plan, supported by both the United States and Britain, has caused outrage among charities at the summit.

UNICEF will hold a McDonald's World Day for Children later in the year, a plan which John Hilary of Save the Children has, with commendable restraint, described as irresponsible, given the record of the American giant in selling junk food.

McDonald's is a company which has ruthlessly targeted the children's market, even inside American schools, for decades.

Given that the eating habits of American kids are generally regarded as something other countries should avoid, a recent survey of children's advertising in the European Union is educational.

American children get a quarter of their vegetable servings as potato chips or French fries. The EU survey found 95 per cent of the food ads encouraged kids to eat foods high in sugar, salt and fat. The company running the most ads aimed at children was - McDonald's.

The growth of what McDonald's has called "global realisation", has been phenomenal. A decade ago it had 3,000 restaurants outside America. Today there are more than 17,000 in 120 countries.

But the link between McDonald's and Coca-Cola is even more intriguing.

The burger chain sells more Coke than anyone else in the world and makes more profit from it than from burgers or chicken nuggets.

Now, with growing alarm over America's obesity and diabetes epidemics, Coca-Cola and other so-called "liquid candy" soft drinks are to be banned in all Los Angeles schools.

With impressive timing, given McDonald's involvement with UNICEF, the decision to impose the ban was taken on Tuesday this week. Similar bans will almost certainly follow across America.

The connection between McDonald's and the Earth Summit may be an outrage but isn't it wonderfully ironic that the Los Angeles ban on Coke in schools has happened in California - where the world's fast food industry was originally invented, all the way back in the Twenties.