A mounting Labour rebellion over Tony Blair's flagship school reforms hit new heights yesterday when John Prescott launched an extraordinary public attack.

The Deputy Prime Minister said he feared giving schools greater freedom would mean a return to the 11-plus and poorer children losing out.

"I'm not totally convinced major reform is necessary," he said in an interview for the Sunday Telegraph.

"Since I was an 11-plus failure, since I do believe that produced a 'first-class/second-class' education system, I fear this is a framework that may do the same.

"I'm somewhat critical of it."

As his comments caused sensation at Westminster, Mr Prescott moved to insist he was not expressing fundamental opposition to the plans.

But he stood by his fears, which until now he has expressed only to colleagues at Cabinet meetings.

Labour critics of key parts of the changes seized on Mr Prescott's decision to break his silence as a clear sign of the depth of discontent in the party.

Martin Salter, who played a key role in the production of a set of alternative policies backed by more than 50 Labour MPs last week, said it was most helpful.

Mr Salter, who quit as a parliamentary aide to Education Minister Jacqui Smith over the issue, said: "I sincerely hope that Tony Blair will take note of the very, very serious paper that myself and colleagues have put together, the comments of Labour Party members, of headteachers, of school governors and, of course, of his own deputy."

Mr Blair faces hard choices over the reforms.

With the number of his backbenchers prepared to vote against the changes said to be in three figures, Mr Blair faces a highly-damaging Commons defeat.

Unless he makes changes - and so far he has expressed his determination to press ahead - he may have to rely on Tory votes to get his policy through.

Shadow Education Secretary David Willetts urged Mr Blair to ignore Mr Prescott's "class war" battle and stand firm.

If the White Paper became a Bill that was the start of serious reform, then he could count on Tory votes to get it through, Mr Willetts said.

Last week, the Prime Minister told MPs: "We will stick with the changes in the White Paper because they are the right changes to make."

But Downing Street has insisted Mr Blair will listen to critics.

Last night, a Department for Education spokesman said: "The issues raised are ones we are aware of.

"Ruth Kelly (Education Secretary) has had a series of meetings with the Parliamentary Labour Party which will continue before the Bill is published.

"For eight years, our education policy has been geared to improving the prospects of working class children.

"None of us can accept a situation where 44 per cent of children do not get five good GCSEs and only 26 per cent on free school meals do."

He continued: "We are determined that the first trusts must benefit schools and children that need them most, and that means making a real difference in deprived communities.

"Trust schools will be able to collaborate and link up together to raise standards with, for example, better performing schools helping schools which are under-performing."