Jamie Oliver today accused Education Secretary Michael Gove of "putting children's future health at risk" as new research showed many academies are now selling junk food.
Over one in four academies are offering crisps and savoury snacks, while around one in six are providing chocolate and sweets, and one in 12 fizzy or energy drinks, according to a study by the School Food Trust (SFT).
The TV chef said that the research has provided "solid evidence" for the first time that nutritional food standards in academies are in danger.
He added that he has written to all MPs asking them to back a parliamentary bid for academies and free schools to be covered by the food standard requirements that apply to other state schools.
Oliver won the support of campaigners last year after raising concerns that academies are not obliged to sign up to tough food regulations introduced by the previous government.
Mr Gove has always maintained that giving academies the choice to opt out of nutritional standards gives them the freedom to do what is best for their students, and said there is no reason to believe these schools will not provide meals that meet the regulations.
Following a meeting with Oliver in June, he asked the SFT to carry out a study of established academies looking at their approach to healthy dinners.
Those findings, published today, reveal that 86% of the 100 academies surveyed reported that they monitored their food against the set standards.
But the report adds that evidence suggests that many were not acting on the results of this monitoring to ensure they met the regulations.
Overall, many academies were offering food that was high in sugar, salt and fat, and in most cases it was on offer in the school canteen, rather than being limited to vending machines or sixth-form areas.
Some 26 academies were providing crisps and other savoury snacks, while 16 were offering chocolate and sweets, the study found.
And 54 were offering cereal bars that are usually high in sugar and classed as confectionery, with a further 82 providing pupils with fruit juice or squash that are either high in sugar or low in fruit.
Researchers concluded: "The findings from the present survey suggest that in the short time that academies have not been required to follow the school food standards, less healthy foods that were restricted from secondary schools are now regularly finding their way back into the dining room."
Oliver said: "For the first time, we have solid evidence from the academies themselves that nutritional standards are in real danger.
"These standards are there for a reason - to help prevent England from sliding further behind when it comes to essential action to fight child obesity and diet-related disease. Mr Gove is putting our children's future health at risk.
"Today, I have written to all MPs asking them to sign Zac Goldsmith's early day motion which demands that academies work within the nutritional guidelines.
"If your MP does not support this motion then you can safely assume that they don't care about the well-being of our children and the future of our country."
