The Food Commission says among the worst products it tested was a Kellogg's Coco-Pops bar which contained a greater proportion of calories from sugar than milk chocolate.

A Kellogg's Rice Krispies bar was found to contain 29% of its calories in the form of saturated fats, which can cause furring of the arteries, and a Mars Tracker banana bar had 43% of its calories from fat.

While sugar eaten in a bowl of cereal tends to be washed away by the milk, when present in sticky cereal bars it encourages maximum damage to teeth, says the report.

High levels

Of the 18 breakfast bars tested, all had higher levels of sugar than nutritionists recommend for a healthy breakfast such as a bowl of cereal with semi-skimmed milk. Ten had higher fat levels.

Yet, many were marketed as wholesome and ideal for school lunchboxes.

The Commission says breakfast sets you up for the day, improves your concentration and limits pre-lunch snacking.

Recent guidelines published by a group of European nutritionists recommend that a healthy diet should not contain more than 30% calories from fat, 10% calories from saturated fat and 10% calories from extrinsic (added) sugars.

Food Commission director Dr Tim Lobstein told BBC News Online: "These bars are marketed on the shelf next to breakfast cereal, but they are more like confectionery.

"We should be eating less fatty, sugary foods."

Helen Giddings, a nutritionist for Kellogg's, told BBC News Online: "Kellogg's cereal and milk bars which are much loved and very popular with consumers, provide essential vitamins and minerals, such as iron and calcium which may otherwise be missed.

"They are in line with government healthy eating guidelines that state that 35% of energy should come from fat.

"It is important to remember there is no such thing as a good or bad food, and all foods can play a part in a healthy balanced diet."