Graham Brady, Tory education spokesman, called for Labour to scrap the system, arguing that it was a waste of taxpayers' money.
Mr Brady said: "This money is being poured into a black hole to fund the processing of failed petitions and failed ballots.
"Not one grammar school has been closed, but massive disruption has been caused for parents and schools.
"Isn't it time Labour conceded that parents want good schools to stay and spend this money in schools where it is needed most?"
The Department for Education and Employment has paid Electoral Reform Services pound;292,000 to manage grammar petitions and ballots since March 1999.
The Ripon ballot cost the DFEE pound;1,780 in printing, postage and administration costs.
Mr Brady said: "Labour has only managed to trigger one ballot, in Ripon, since the scheme was introduced in March 1999 but parents voted with common sense."
But anti-selection activists have blamed the complexity of the system, which involves collecting parents' signatures, for its failure.
A spokesman for Mr Blunkett said that the money was a fraction of that spent on grant-maintained school ballots under the Tories. He said: "Allowing parents to decide the future of admissions arrangements was one of our manifesto commitments and we have a duty to ensure that it is managed properly."