Academies and free schools which opt not to follow national regulations are failing in their moral duty to ensure pupils receive healthy dinners, according to the Local Government Association (LGA).
It said it was concerned that more than a million youngsters attending these schools could be eating poor quality dinners.
It comes as new figures show there are almost 250 academies open across Yorkshire.
The LGA has issued a fresh call to the Government to introduce a single standard that applies to all schools to make sure that every youngster has access to a healthy lunch. Academies and free schools are exempt from the rules which have been in place for more than five years.
The number of academies has increased dramatically since the coalition expanded the programme in 2010. Originally they were set up as new schools based in new buildings with backing from an outside sponsor but now state schools are able to convert.
New Department for Education figures show that there are now more than 2,600 academies open – with a further 500 set to convert to academy status.
This includes 243 across Yorkshire 178 of which have converted since the Government encouraged all state schools to opt out of local authority control and become autonomously-run academies.
The LGA statement comes just months before councils are to take on more responsibility for public health, including tackling childhood obesity and overseeing the national child measurement service which takes the height and weight of children in reception and the final year of primary school.
David Simmonds, chairman of LGA’s children and young people board, said: “We know parents want school lunches that are healthy and nutritious, whatever type of school their child attends. School autonomy is supposed to drive up standards but in the case of school meals, we now have a two-tier system where one type of school can effectively exempt pupils from healthy choices and instead sell fatty and sugary foods.
“This threatens to seriously impact on the health and educational attainment of our children.
“As champions for parents and children, councils with new public health responsibilities will want to hold all schools to account if they are ducking their moral duty to give students the best chance of living a happy and healthy life.
“History shows us that voluntary guidelines alone do not work to drive up standards. We now need government to do its part by introducing an acceptable food standard that will allow councils to hold all schools to account for the nutritional quality of food they serve their pupils.”
Academies and free schools do not have to adhere to the same nutritional standards, introduced by the last government, that apply to other state schools.
Education Secretary Michael Gove has always maintained that giving these schools the choice to opt out gives them the freedom to do what is best for their students.
However campaigners, including TV chef Jamie Oliver, have raised concerns about the exemption, suggesting it will put children’s health at risk.