Huge numbers of children will lose their free hot lunches under Conservative plans to ease school funding cuts, Nick Clegg has warned.

Theresa May was branded “the lunch snatcher” after unveiling plans to replace universal lunchtime meals for infants with free breakfasts for every pupil up to the age of 11.

The Tories said children from poorer families would continue to get free hot lunches – as well as free breakfasts – throughout their education.

And they argued that evidence showed breakfast is as effective at helping children learn at school as a hot lunch, while being delivered at a tenth of the cost at about £60m a year.

The switch would provide the bulk of a £1bn cash injection for education, at a time when schools are facing huge cuts and laying off teachers.

But Mr Clegg, the architect of the free lunches policy as deputy prime minister in the Coalition, attacked the move as “cynical”.

The former Liberal Democrat leader pointed out that, when means-tested, free lunches failed to reach all pupils living below the breadline.

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“Free infant lunches policy was saving millions of struggling families over £450. Breakfasts covers fewer children. Cheaper for govt. Cynical,” Mr Clegg tweeted.

“4 in 10 kids who DIDN’T receive free lunches prior to infant provision were officially in poverty. So much for compassionate Conservatives.”

Sarah Olney, the Lib Dem education spokeswoman, said: “Margaret Thatcher was know as the ‘milk snatcher’. Theresa May will go down as the ‘lunch snatcher’.”

The Conservatives can point to research suggesting Year Two children in schools with breakfast clubs progress by about an extra two months, compared with those in schools without.

The Magic Breakfast project, which carried out the research, said in a statement: “These positive results would be unlikely to occur by chance.

“The findings suggest that it is not just eating breakfast that delivers improvements, but attending a breakfast club.”

However, the policy may cause problems for schools, struggling with staffing reductions, which will be expected to provide canteen staff to prepare food and teachers to supervise.

Furthermore, the Conservatives were only able to say that the £1bn-a-year extra funding would prevent any school losing out “in cash terms” from a controversial new national funding formula.

That means some could still be worse off after inflation and it is unclear how much of the current funding cuts might now be avoided.

A Conservative spokesman said: “This extra money means no child will lose out.”

Both Labour and the Lib Dems have pledged to extend free school meals to all primary school children, marking out a sharp divide with the Tories on the policy.