Anyone swapping a traditional cooked breakfast for a bowl of cereal for health reasons may end up eating food with as much sugar as a chocolate bar, according to a survey. Which? said that many breakfast cereals were stuffed with sugar and salt despite many being aimed at children or health-conscious shoppers.

The organisation said that the two sweetest products it tested, Asda and Morrisons' Golden Puffs, had 55 per cent sugar - almost as much as a Mars Bar. And despite its healthy image, Kellogg's All-Bran shared with another Morrisons product the distinction of having the most salt per suggested portion.

One nutty wholegrain cereal, Jordans Country Crisp Four Nut Combo, had as much fat per serving as a McDonald's bacon roll. Which? assessed the healthiness of 275 different cereals from manufacturers such as Kellogg's and the big four supermarket chains, Tesco, Sainsbury's, Asda and Morrisons.

It said that, by the criteria used by the Food Standards Agency (FSA) to assess the nutrient levels of food, more than three- quarters of products were high in sugar and just under a fifth had high levels of salt.

Levels of saturated fat were mostly low to medium, with 7 per cent warranting a "red light" under the FSA's traffic light labelling scheme.

Which? found it "particularly worrying" that 88 per cent of cereals targeted at children were high in sugar. Thirteen per cent were high in salt and 10 per cent high in saturated fat.

Overall, nine cereals were found to have four teaspoons of sugar per suggested portion.

Anyone eating Asda Hawaiian Crunch, Sainsbury's Crunchy Oat or Asda Passion Fruit Crisp would consume as much saturated fat as that found in two fried eggs.

The three worst offenders overall were Quaker Oatso Simple Kids, Kellogg's Coco Pops Straws and Mornflake Pecan and Maple Crisp, which had red lights for both sugar and saturated fat. Kellogg's Coco Pops Straws had the same amount of sugar as a two-finger Kit Kat.

Sue Davies, the chief policy adviser at Which?, said: "While manufacturers have made some efforts to reduce the salt levels in their breakfast cereals, we still found lots of products with high levels of salt as well as high levels of sugar.

"Despite their healthy image, some cereals also have high levels of fat and saturates. And with so much public concern about obesity and diet-related disease, we're particularly concerned that most cereals marketed to children are still high in sugar, and many are high in salt too."

Which? said that manufacturers had made little progress since 2004, when the organisation surveyed 100 brands for a report called Cereal Offenders. But because of opposition from food companies, few breakfast cereals will carry the new national traffic light labelling, which shows colour codes for levels of sugar, salt, fat, and saturated fat.

Tesco, Morrisons, and big food companies such as Nestlé and Kellogg's instead plan to use labels showing the percentage a product contributes to nutritional guideline daily allowances.