Education Secretary Michael Gove was accused today of wasting millions of pounds of public money on “pet projects which do not benefit pupils”.
Labour said that, according to its figures, the Government had spent at least £2.3 million on free schools which it claimed were either not opening, or lack support.
The Government immediately refuted the accusation, insisting it would "never gamble with the future of our children" and that the figures had been "grossly exaggerated".
Free schools "are overwhelmingly popular" with parents and are opening quicker, and more cheaply than previous school schemes, the Department for Education (DfE) said.
In a letter to Mr Gove, shadow education secretary Stephen Twigg said: "I hope you will agree that it is imperative to ensure that every penny of taxpayers' money is wisely spent.
"While families in Britain are feeling the squeeze brought about by the double-dip recession, it is surely right that the Government spends their money in a responsible manner.
"You said in May this year that 'I have been determined to use the capital funding at my disposal to best effect, seeking value for money and efficiency from every pound spent'.
"I cannot see how you can justify this claim, when it emerges that millions of pounds of public money have been wasted by your Department on schools which either failed to open or lack local support from parents."
Mr Twigg said Labour's own figures suggest that "at least £2.3 million has been wasted on pet projects".
The letter cites the One In A Million Free School in Bradford, West Yorkshire, Beccles Free School in Suffolk, and the Riverdale Primary School in west London.
It was revealed earlier this week that the Government had decided to withdraw funding for the One In A Million school just a week before it was due to open.
A decision is still to be taken on whether the charity-run school will open next year instead.
The Riverdale Primary School is now not opening.
In June it emerged that Beccles Free School, which is scheduled to open this autumn, had received just 37 applications for 162 places, although the DfE said it now has 68 pupils.
In his letter, Mr Twigg claimed that £2 million has been spent on Beccles.
Mr Twigg also claimed that "a number of free school projects have collapsed, but it is unclear how much was spent on these projects".
He cited the Chorley Career and Sixth Form Academy, Rotherham Central Free School in South Yorkshire and the Newham Free Academy in east London.
The DfE said that early decisions had been taken to not go ahead with these three projects, and that no capital had been spent on the Rotherham and Newham schools.
Mr Twigg asked Mr Gove in his letter to explain how many of the free schools originally expected to open this September will open as planned, how much money has been spent in total, and individually, on free schools that will not open next month, and the reasons for projects collapsing.
A DfE spokeswoman said: "These figures are grossly exaggerated. Beccles Free School will open as planned this September with 68 pupils, and One In A Million Free School is considering deferring until next year.
"The truth is free schools are opening more quickly and have been delivered more cheaply than previous schemes. Free schools are also proving overwhelmingly popular with parents - the vast majority of those opened in 2011 are already full.
"We will never gamble with the future of our children and make no apologies for setting high standards. We would never allow a free school to open which didn't satisfy the needs of the local community and meet our strict criteria."
A spokesman for Mr Gove added: "Stephen Twigg's effort is back- of-the-envelope stuff that doesn't stack up.
"Beccles Free School actually has double as many pupils as he claims which he could have found out by simply Googling.
"The real scandal is the millions upon millions the Labour government wasted on Building Schools For The Future, which Twigg himself has admitted didn't deliver value for money."
As of October last year, 79 free schools and university technical colleges (UTC) had been approved to open from this September onwards.