Council leaders have called for loopholes to be closed that mean 4,000 schools do not have to adhere to new standards on healthy meals.

Stricter rules that came into force this week restrict the amount of fried and fatty food served up to pupils and ensure at least one portion of vegetables or salad is available every day.

But they do not apply to schools that became academies between 2010-14. The Local Government Association (LGA) said this means more than two million children – one in four pupils – are at schools which do not have to comply. It wants the standards to be mandatory across all schools.

Cllr David Simmonds, chair of the LGA’s children and young people’s board, said: ‘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 chose to sell fatty and sugary foods. With ample evidence that good food supports good learning in the classroom, all schools should meet the same high standards.

‘It is a particular worry given that for the many children who receive free school meals, lunch is often their main meal of the day. Councils are responsible for the challenge of tackling obesity and poor diet as part of our public health responsibilities and we do not want to see junk food on the menu in any school.

‘No school should be exempt from these important standards and we urge the Government to make regulations on school food mandatory to ensure every child receives healthy and nutritious food at school.’