Tessa Jowell has called on the government to give "very strong leadership" against the increase in childhood obesity.

The culture secretary insisted that Ofcom, the new communications watchdog, will be given tougher powers to regulate food advertisements.

Ministers should also be more proactive in getting people fit, she argued in an interview with The Guardian newspaper in December.

"Our example is Finland, where 10 or 15 years ago, if you looked at their rate of coronary heart disease, it was relatively high and about 30 per cent of the population were physically active," she said.

But now "70 per cent of Finns are physically active and their rate of coronary heart disease has come down, and they are not facing the sort of obesity crisis that we are", said Jowell.

"Our ambition over the next 15 to 20 years is to achieve similar progress," she added.

Jowell also claimed that a tighter advertising code for Ofcom was in the food industry's interest. "I hope that it will be tightened up...and I hope it will reflect the willingness of the food manufacturers to promote healthy eating," she said. "It is in the industry's interest to work constructively in the public interest.

"We are determined that we are going to provide this proactive context."

Figures show that 8.5 per cent of six-year olds and 15 per cent of 15-year old children are considered clinically obese.

But the culture secretary's comments have already been rejected by fast food industry leaders. "There is already a strict code in existence which the food and industry has an exemplary record of obeying," said a spokeswoman for the Food and Drink Federation.

However, a consultation on the issue will be completed by the Food Standards Agency in the new year. Options being discussed include a ban on advertisements aimed at pre-school children, and limits on the use of cartoon characters and children's television presenters in such commercials.