She demanded advertisers took responsibility and did something to stop the rise in junk food diets. And now culture secretary Tessa Jowell has got direct action after the head of one of the country's biggest advertising poster companies pledged to provide free bicycles to Londoners.

In an extraordinary gesture designed to show the government it was serious about doing its bit the fight against obesity, Jean-Francois Decaux, the head of outdoor advertising company JC Decaux, said he would deliver on his promise if the government did something to improve the capital's cycle routes.

He was speaking after Ms Jowell urged advertisers to use their "famous creativity" to come up with solutions to Britain's obesity crisis.

Mr Decaux said it was not an empty gesture designed to win the company column inches, and referred to the success of similar schemes in Austria and Germany, where the group has supplied 3,000 free bicycles.

"People get the first hour free then pay two euros per hour and the scheme is funded through advertising billboards," said Mr Decaux. "My suggestion would be that the government builds the bicycle routes London needs and we will provide the bicycles."

JC Decaux has a history of innovative advertising ideas for city centres. It funded the building of hundreds of bus shelters across the UK, and was also behind the invention of the so-called "super loos'" that have largely replaced municipal toilets in Britain.

Mr Decaux said the lack of cycle routes meant London was not yet a safe city for cyclists. But he said his company would be happy to extend its scheme to the UK if the government was prepared to improve the capital's cycle routes.

Ms Jowell refused to be drawn on the issue, saying only that she hoped the rest of the industry would be equally creative in its approach to the problem.

The culture secretary today appeared to rule out an outright ban on junk food advertising, saying there were "no quick answers" to the problem of obesity.

But she called on the industry to come up with its own solution.

"I know that you have already done a great deal. But we cannot afford to stand still. Because the danger is that the argument is won by default by those who call for an outright advertising ban," she told a conference of advertisers today.

"So this is your challenge. Prove again that advertising need not be an adversary of those who want a healthier Britain... do it by using the creativity you are famous for to put your products in a context of healthy eating."

Critics of the Decaux plan may point out that similar communal bike schemes in Britain have not always proved successful.

Ten years ago Cambridge introduced a park and ride-style "green bike scheme" to help relieve congestion, but the free cycles were targeted by organised thieves. Within days of the scheme being put in place, nearly all of the 300 bicycles had been stolen. A second attempt proved just as fruitless, and the scheme was abandoned within a year.

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