The unions were able this week to seize upon Tony Blair’s careless use of statistics to accuse Labour of unfair teacher-bashing.

At the launch of Labour’s reform package for raising standards in schools, the party leader claimed that 30 per cent of schools are failing.

The claim unleashed a barrage of criticism from the teacher unions, already irritated by what they saw as an over-emphasis on policies designed to speed up the sacking of poor teachers.

They were able to point out that Mr Blair’s figures are not borne out by evidence from the Office for Standards in Education. There are around 100 schools - or 2 per cent - that have been judged by OFSTED to be failing to provide adequate education. A further 10 per cent are being monitored because they have serious weaknesses.

Mr Blair appears to have used a figure given in inspectors’ reports for the 30 per cent of lessons considered to be unsatisfactory, but there was no attempt by his office to correct his original statement.

The dispute over the figures added weight to the argument from John Sutton, general secretary of the Secondary Heads Association, and David Hart, general secretary of the National Association of Head Teachers, that Labour was intent on emphasising failure and keen to be seen to be “teacher-bashing”.

According to Mr Hart, the positive aspects of Labour’s plans had been overshadowed by the talk of failing schools, failing heads and failing teachers.

Mr Hart maintains a Labour government would not be able to speed up the process for getting rid of poor teachers without changing employment legislation.

“Heads are not shrinking from the task of tackling incompetency. The problem is that there has to be a balance between the needs of pupils and the necessity to treat individual members of staff with fairness,” he says.

Criticism of Labour’s approach was not confined to the unions. Among academics, David Reynolds, professor of education at Newcastle, was sceptical about the prospects for taking action against weak teachers.

“The problem is that we know remarkably little about teacher effectiveness. Any performance indicator that linked poor teaching with academic results would have to be very complicated,” he says.

The other problem area for Labour, he says, is the reliance on parent contracts. The party wants parents to sign up for home-school contracts which will set out parental responsibility for seeing that homework is done and that pupils do not play truant. Such contracts, says Mr Reynolds, are unenforceable because nothing could be done about the parents that refuse to take part.

Government ministers take the line that Labour has at last come around to Conservative thinking on education. Gillian Shephard, the Education and Employment Secretary, points to Labour’s backing for specialist schools, testing and inspection.

However, much of the new policy paper reflects the debt Labour owes to education professionals, particularly Michael Barber, dean of new initiatives at the Institute of Education at London University. The stress on raising standards moves Labour on to the high ground traditionally held by the Conservatives and distances the party from the unions.

A mark of how far Labour has shifted is that Dr Madsen Pirie of the right-wing Adam Smith Institute can claim that the party has taken bold steps in adapting its policies on the need to close failing schools and its stress on the need for parental responsibility.

That is not an endorsement likely to provide much comfort for Mr Blunkett.