Some blueberry muffins have more sugar than a can of Coke

Your morning treat could include a day's worth of sugar, according to new research.

A joint study by Action on Sugar and the Obesity Health Alliance found that some blueberry muffins contain up to ten teaspoons of sugar – more than a can of Coke.

The recommended daily limit for adults is seven teaspoons. For children it is lower: those aged four to six years should have no more than five teaspoons while no more than six spoons are recommended for those aged seven to ten.

Researchers who examined 28 muffins sold in food outlets in train stations and supermarkets found 61% of them contained six teaspoons of sugar or more. McDonald’s muffins had 32g, equal to eight teaspoons, while Pret A Manger’s weighed in at 30.5g. The most sugar was found in Costa’s muffins, which have 40g of sugar - the same as ten teaspoons.

Action on Sugar and the Obesity Health Alliance has called for manufacturers to reduce sugar by 20% by 2020, in line with government targets. The Obesity Health Alliance said: “We may think [blueberry muffins] are healthy yet the figures suggest otherwise. Industry must step up to the plate and take responsibility.”

The two organisations are calling on “out of home outlets” to be clearer about the nutrition content of their products by introducing “traffic light” nutrition labelling available to consumers at the point of sale.

The British Retail Consortium, which represents food retailers, told the BBC that its members were "actively engaged" in Public Health England's sugar reduction strategy.