Tim Yeo, the party’s education spokesman, said middle-class parents should not be able to jump the queue into popular state schools by moving into the area.

He told the National Union of Teachers conference in Harrogate: “I want all parents to have the kind of choice which at present is only available to those who can afford to choose where they live.”

Oversubscribed schools would be able to select on other criteria, such as academic ability or aptitude in sport or the arts, his office later confirmed.

The Tories want to introduce pupil passports in which money for state schooling follows the child. They would also make it easier for successful schools to expand, by abolishing the surplus places rule. Mr Yeo admitted surplus places entail costs, but said they were necessary for the system to work.

But Professor Alan Smithers, of Liverpool university, said: “If schools can’t select by proximity they will select by religious affliation, academic testing or some other factor. The problem is the same, while some schools are a lot more popular than others and parents compete to get into them, how do you sort out allocations fairly?

“I don’t think the Conservatives offer a solution other than popular schools will get bigger, but there is a limit to how far they can expand.”

Good schools can raise house prices by as much as pound;40,000. The National Association of Estate Agents said that the Tory policy could knock some of the premium from homes near popular schools, but it would lead to price rises in streets just outside the catchment area.

Mr Yeo also told the conference that the Tories would examine the possibility of granting anonymity for accused teachers, to be lifted only if there was a conviction.

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