Labels give information on how many calories the food contains

The calorie counts used as the foundation for diet plans and healthy-eating guidance for the past 18 years may be wrong, a report suggests.

The recommended daily intake of calories could be increased by up to 16%, a draft report by the Scientific Advisory Committee on Nutrition said.

Intake levels are currently 2,000 calories for women and 2,500 for men.

But the panel stresses that people should only eat more if they exercise more, given rising levels of obesity.

The committee says its report provides a much more accurate assessment of how energy can be burnt off through physical activity.

A 16% increase would mean that adults already sticking to the recommended levels could consume an extra 400 calories a day, equivalent to an average-sized cheeseburger.

The proposals, seen by The Times and The Grocer magazine, are due to go out for a 14-week consultation period.

Final recommendations will then be made after that time.

Health campaigners say the Department of Health and the Food Standards Agency could seek to "sweep this report under the carpet" in a bid to avoid sending out mixed messages in the middle of an obesity epidemic.

Tam Fry, of the National Obesity Forum, said it was a "dangerous assumption" to say that adults could safely consume an extra 400 calories a day.

"This is not a green light to eat yourself silly," he said.

Update June 2011: Following a ruling by the BBC's Editorial Complaints Unit, this story has been amended to make clear that only those already sticking to recommended levels should consider increasing their intake. More details can be found here.