Kellogg's has slammed a study by the FSA that asked consumers for their reaction to the sugar content of breakfast cereals - based on a 100g portion.

The FSA ran the survey to help determine nutrition criteria for its traffic light labelling of breakfast cereals.

Respondents were presented with cereal packets mocked up to include the FSA's nutrition signposting. In most cases the packs carried a red light to indicate a high sugar content.

Participants said they were surprised by the high levels of sugar in many breakfast cereals.

But Chris Wermann, director of corporate affairs at Kellogg's, which uses GDA labelling on its packs, said the research was misleading because people tended to eat cereal in 30g portions, not 100g.

"When you look at the FSA's view of what constitutes a portion size and what our research tells us, we are seeing a huge discrepancy. Using a 30g to 50g portion would show that most cereals contain no more than 12% sugar. Considering breakfast should contribute around 25% of the day's nutrients, this is not a huge amount."

The FSA said: "The key objective is easy-to-understand labels, which help consumers choose healthier products."