The letter, which was launched on Thursday 22 September by The Mirror and the National Education Union, is urging new Prime Minister Liz Truss to ensure no children in England are left hungry. A report by the Food Foundation earlier this year found that as many as 2.6m children lived in households that struggled to access food.
The letter has been signed by London Mayor Sadiq Khan, Greater Manchester Mayor Andy Burnham and TV presenter Gary Lineker.
Children's Food Campaign co-ordinator Barbara Crowther said: "There is an urgent need to provide targeted support for families with children who are facing increasing food and energy bills. We are rightly proud of our fantastic free education system, yet we continue to subject children to means testing for this one part of their school day, against a threshold so low that 800,000 children living in poverty in England are not even eligible.
“Decent nutrition is fundamental to children's ability to concentrate, learn and thrive in school. Not only would expanding school meal provision effectively put money back into the pockets of hard working families, it could be a significant boost to all the food providers and caterers providing those meals, bringing more jobs and prosperity into the surrounding communities.
“The Prime Minister, Chancellor and Education Secretary should seriously consider a rapid expansion of school meal provision as part of any plans to address the cost of living and promote business growth across the nation."