Plans to scrap free school milk scrapped amid claims of policy 'made on the hoof'

Number 10 stamped on the idea despite Health Minister Anne Milton insisting the provision for under-fives was ineffective and too expensive.

The volte-face happened just hours after the proposal emerged publicly, and so quickly that Universities Minister David Willetts was left floundering in a television interview.

The mooted cut could also have caused more friction within the coalition as senior Liberal Democrats have praised the provision of free milk.

The Nursery Milk scheme allows children under five in approved day care to receive a third of as pint of milk free of charge each day. It dates from 1940, when milk was issued to pregnant women and young children to protect against wartime food shortages.

In a leaked letter to the Scottish Government, Ms Milton said the cost had almost doubled in the last five years to some 50m and there was "no evidence that it improves the health of very young children". She said abolition would be fiercely opposed but added: "This should not prevent us from ending an ineffective universal measure."

Ms Milton suggested that the value of Healthy Start vouchers – which are given to pregnant women and children under four and can be used to buy milk or fresh fruit and vegetables – could be increased to compensate.

Asked about the plan on the BBC's Andrew Marr Show Mr Willetts confirmed it was on the table. "We're having a comprehensive spending review, so we are looking at a whole range of options."

But even as the Minister spoke, Downing Street was making clear to reporters that David Cameron did not like the idea of cancelling free milk and it would "not be happening".

When this information was conveyed to Mr Willetts on screen, he replied there was an process of assessing options. "It is inevitable that if you go through those decisions some options go ahead and others don't."

Labour leadership contender Ed Balls, MP for Morley and Outwood in West Yorkshire, said: "This is a coalition in chaos, making policy on the hoof."