Conservative-controlled Kent - which has the largest concentration of grammar schools in England - has long said that ending selection in the county could cost it �150m.

Ripon is also a target for anti-selection campaigners

The Conservative Party nationally even extrapolated from this figure to say that ending selection across England could cost �500m, although inquiries of other education authorities by News Online indicated that there might actually be a net saving.

The local anti-selection campaign in Kent, Stop the 11-Plus (Step), has repeatedly challenged the �150m figure. It complained to the Department for Education in London about the matter.

In a reply this week, the department said it did "remain concerned at the use of the �150m figure as the estimated cost of reorganisation in Kent."

David Shand, of the department's grammar school ballots team, referred in his letter to comments by the vice-chairman of Kent's education committee, Leyland Ridings.

"The report Mr Ridings quotes highlighted several possible options, of which the 'worst case scenario' suggested that costs could possibly reach �150m," he wrote.

Context

"The department feels that this is somewhat different from Mr Riding's suggestion and that there is a risk that the �150m could be misinterpreted as being the actual cost following any ballot in favour of ending selection.

"We have therefore asked that any future material which uses this figure makes the context clear."

The whole issue of selection was raised by the Conservative Party in a Commons debate on Wednesday morning.

Allowing parents to vote on whether selective schools in their area should become comprehensives was a "one-way ratchet" that actually denied choice, said Tory MP Graham Brady.

Graham Brady: "One-way ratchet"

Opening the short debate, Mr Brady complained that the complex regulations allowing a parental ballot to end selection contained no mechanism to allow parents to demand that more schools convert to selective status.

"Now we are stuck with a flawed procedure which is loaded against the remaining grammar schools," he said.

Remaining grammar schools had been placed in a "state of peril".

"It certainly isn't true when Labour MPs say this is about parental choice - parents are free to chose not to have a grammar school but they not free to have a grammar school."

One Labour MP, Ben Chapman, said he had attended a grammar school and would vote to keep them.

"If our grammar schools are doing a good job ... let's leave well alone. If they ain't broke, they don't need fixing."

John Bercow: "Labour hooligans"

The Conservative education spokesman John Bercow said Tories would fight the government's ballot plans which he warned could lead to the scrapping of some of the best schools in the country.

"It is a centrally co-ordinated campaign by egalitarian hooligans and educational vandals who want to destroy what exists and what works, in favour of an untried and untested method which happens to conform to the egalitarian prejudices of members of the Labour Party," he said.

Estelle Morris: "Tories let 643 grammars close when in power"

It was, he said, "a backdoor method of destroying the best schools in this country."

The Education Minister Estelle Morris said it was no longer good enough to give just the top 25% of children a good education. The government was determined to deliver the best for all.

"The challenge which faces this nation now and the challenge which faces the education service is no longer good education for the few and the top 25%," she said.