A Conservative pledge to scrap free school dinners for infants has been condemned as an "absolute betrayal" as the party came under fresh pressure from headteachers and celebrity campaigners.
School leaders warned that hundreds of millions of pounds pumped into funding the free dinners is set to be wasted, and that schools have been left "utterly perplexed" by the move.
They pointed to a letter sent to schools by former Education Secretary Michael Gove and former Schools Minister David Laws in 2014, which highlighted the health and academic benefits of universal free dinners and insisted the meals were "a serious and long-term policy commitment".
Celebrity chef Jamie Oliver said the Tory policy was "misguided", while Henry Dimbleby, who co-authored the School Food Plan for the coalition government - which recommended free lunches - described it as an "absolute betrayal".
In its General Election manifesto, the Conservatives pledged to scrap universal free lunches for infant school children in England, but said they would instead offer a free breakfast for all primary school pupils.
Evidence shows that a free school breakfast is as effective at helping children learn as a hot meal at lunch, the party said, and can be delivered at a tenth of the cost, at around £60 million a year.
But experts have calculated that the price of free breakfasts could run into hundreds of millions of pounds, and the Conservatives have acknowledged that if many more children take up the offer than expected, costs could rise.
Free lunches for infants were introduced in September 2014.
The letter from Mr Gove and Mr Laws, sent to school leaders in January of that year, said schools could plan confidently for the policy "in the knowledge that we are making a serious and long-term policy commitment".
The missive, first reported by the Evening Standard, went on to say pilot projects had shown that universal free meals have "significant benefits for both individual children and for the broader life of the school".
Russell Hobby, general secretary of the National Association of Head Teachers (NAHT) said: "In 2014, the evidence and the ambition for this policy were both made clear to us. In the letter, school leaders were also told to expect that the policy would be extended to 'additional year groups in the future'. On the basis of these assurances, school leaders invested heavily in newer kitchens, more staff and extra equipment.
"Three years later, these proposals are set to be ripped up, leaving those of us with the best interests of children at heart utterly perplexed.
"It would be a huge mistake to end universal infant free school meals without any proper evaluation of the project. Hundreds of millions of pounds of investment is set to be wasted with no clear rationale apart from a desire to save money."
Mr Dimbleby, co-founder of the Leon restaurant chain, said: "The taxpayer spent £180m on installing and refurbing school kitchens, and the schools invested their own precious funds too. To axe infant free school meals now is an absolute betrayal, not only of our children, but of our headteachers, who have been misled and whose budgets are already stretched.
"The proposal to invest £60m instead on free breakfast for all children would work out at a measly 7p per breakfast. A handful of sugary cereal will not sustain a child for a day - I challenge anyone to show me a healthy, filling breakfast that could be made for that amount."
Oliver said that children need to be fed well to help them reach their potential.
"Replacing their access to a proper balanced lunch, packed with the veg and nutrients kids need, with a 7p breakfast is just bonkers," he said.
He added: "Swapping from free lunch to a cheap, probably sugary, breakfast is misguided, mean, and a false economy."
A Conservative spokesman said: "These fears are unfounded and it is disappointing to see them whipped up as a scare campaign.
"Our plans guarantee that every primary school child will have access to a free breakfast at school, which experts say provides the same benefits as a free lunch, and we'll continue to ensure school lunches are free for those who need them. So the poorest children will get not one but two free school meals per day."