UK health campaigners have criticised scientific claims that suggest calorie intake should be increased by up to 16%.

A draft report by the Scientific Advisory Committee on Nutrition (SACN) claimed the calorie counts used as the foundation for diet plans and healthy-eating guidance for the past 18 years may be wrong.

Intake levels are currently 2,000 calories for women and 2,500 for men. A 16% increase would mean that adults could consume an extra 400 calories a day and women an extra 300 calories.

The report on "energy requirements" emphasises that people should only eat more if they exercise more, given rising levels of obesity.

However, Tam Fry, of the National Obesity Forum, said that while, as a piece of academic research the report is "completely justified", it is "disastrous" that it should be appearing at this time.

"The scientific committee have obviously gone back to what they wrote in 1991 and re-evaluated it on the basis of physical activity but it is disastrous that it should be appearing at this time," Fry said. 

"The reason being is because those people that you really want to eat less will be seen to be given the green light to eat more because they will just look at the headlines which say it's ok to add calories to your diet per day."

Fry added: "People will say, 'ok that's fine I'll have another cheeseburger' or 'I'll have another four chocolate biscuits'. Therefore, the messages are really confusing and unfortunately, with no ill intent. SACN are perfectly within their rights to say what they did say, but the media naturally has picked up on the fact that they are allowing 400 more calories per day."

Fry said the industry will have to "wait and see" what effects the report, when published, will have on obesity levels.

"I really hope it will have no great effect but I'm really not holding my breath because already people are looking happier in the knowledge that if they do have that extra cheeseburger then they are in the requirements but of course that is inaccurate.

"You can't expect people to read a 200-page document to find out exactly what is intended by the document, all they're going to see is the headlines in the media."

The 14-week scientific consultation will run until 11 February 2010 and final recommendations will be made after that time.