Regulator Ofcom has outlawed ads for foods high in fat, salt and sugar in an effort to tackle soaring childhood obesity rates.

Last year, a crackdown was introduced during programmes made to appeal to seven to nine-year-olds.

Health campaigners had wanted a total ban before the 9pm watershed.

The move comes as a survey suggested the UK was the country most keen on junk food, closely followed by the United States.

A poll by market research firm Synovate, which questioned 9,000 people in 13 nations, found that 45 per cent of Brits said: “I like the taste of fast food too much to give it up.”

Neil Donnelly, head of dietetics at Blackpool Victoria Hospital, said he felt the ban was a step in the right direction.

He sees obese children at his clinic and said he has seen a recent rise in the number of youngsters with diabetes – something relatively unheard of 20 years ago.

He said: “The view among the scientific community is that this would be a relatively good thing, as we have to do something about the problem of childhood obesity.

“Some might argue it’s a bit nanny state, and the evidence as to how successful this has been in other countries is a bit limited, but I think most people will see why this move is needed.

“Parents also have a role to play in setting an example and not buying junk food for their children.

“I think it’s also important to reduce the amount of time children are spending watching TV – so they wouldn’t have chance to see the adverts – and encourage them to do something more active.

“Many of the obese youngsters I see have already got into that mindset of being an obese person.

“I think banning the advertising of junk food on TV for under 16s is a necessary step, given the health situation this country is facing.”

But Cary Cooper, professor of psychology and health at Lancaster University, said he felt the ban would have some effect, but it would only be minimal.

He said: “We do live in a multimedia age, particularly kids. I think this ban will be partially effective, because kids, especially up to the age of 16, are heavily influenced by television.

“But there are other mediums, for example, on-line, where children can access this sort of advertising. And of course, one of the major influences on youngsters is their peer group.

“I suspect the junk food companies might find other ways of reaching children, such as sponsoring events. The more responsible firms won’t do that of course.

“What could happen is that the junk food companies might be forced to make their food healthier, which would be an improvement.

“I think the effect of this ban will be marginal. We live in a culture where things move fast and fast food is popular among both adults and children.”

Broadcasters claim programme quality will be hit by the loss of an estimated £39m in advertising revenue.