DEFIANT Education Secretary Ruth Kelly, the MP for Bolton West, insisted on Thursday that Britain had "some of the toughest child protection laws in Europe".

But she was forced to admit to MPs that she did not know the "precise number" of cases where people on the sex offenders register had been allowed to take up teaching jobs.

She told the Commons that finding out the number was one of the purposes of an "exhaustive review" she has set up in the wake of the case of Paul Reeve.

Opposition MPs said she should 'consider her position'.

And parents demanded an apology from Ms Kelly after she revealed that her department had allowed more adults on the sex offenders' register to work in schools.

The pressure on Ms Kelly brought an unprecedented vote of confidence in her from Downing Street.

Tony Blair was forced to insist she would not lose her job.

The Prime Minister's official spokesman said Mr Blair wanted her to stay in her job to see through controversial education reforms.

Ms Kelly came under fresh pressure when Sir Michael Bichard, who headed the inquiry into the Soham killings, said he was 'disappointed' recommended new safeguards to protect schoolchildren had still not been introduced.

Ms Kelly's troubles were added to by former Labour leader Neil Kinnock, who savaged controversial school reforms.

The normally loyal peer said plans for new independent state schools were 'at best a distraction and at worst dangerous'.

The controversy over sex offenders grew on Wednesday as Ms Kelly announced an urgent review after confirming 'a small number of cases' similar to that of Norfolk PE teacher Paul Reeve. The Government cleared Mr Reeve to work at the Hewett School in Norwich last year, even though he received a police caution for accessing banned images of children on the internet.

It is thought that about 10 similar cases may have been identified so far. The Conservatives said the fresh details cast further doubt on Ms Kelly's judgment.

In a written statement to MPs, Ms Kelly insisted children's safety was 'a top priority'.

She said she took full responsibility for all decisions taken in her department on whether individuals should be placed on List 99, the Education Department's own list of those barred from working in schools.

She said: "Initial inquiries indicate that there have been a small number of cases where ministers have made the decision not to include on List 99 an individual on the sex offenders' register.

"It is of the utmost importance that the House and wider public are not misled by any information put into the public domain.

"I have therefore decided to commission, as a matter of urgency, an exhaustive review of all such cases since the introduction of the sex offenders register, the decision-making process surrounding such cases and any immediate policy implications."

Ministers at the Department for Education and Skills decided last year that the risks of allowing Mr Reeve to work at the school were 'acceptable'.

Mr Reeve worked for eight days last month before he left when police raised the alarm.

It was thought that the decision to give him clearance was taken by a junior minister on duty at the DfES rather than Ms Kelly personally.

In her statement, Ms Kelly promised that 'with immediate effect' she would consider any similar cases in person.

Later, Ms Kelly declined to say how many more cases like that of Mr Reeve there were before the review had been completed.

Margaret Morrissey, spokeswoman for the National Confederation of Parent Teacher Associations, said the news that there were others on the sex offenders register working in schools was 'terrifying'.

"Ruth Kelly should apologise for allowing people on the sex offenders' register to work in our schools,' she said.

"She is going to have to look at her own conscience as a mother and politician over this issue.'

Shadow Education Secretary David Willetts accused Ms Kelly of 'ducking and diving'.

"It seems from her statement that she is now trying to shift responsibility to others by saying that from now on she will consider cases personally,' he said.

"The more this affair drags on, the more serious are the concerns about the Education Secretary's judgment.

'We still need straight answers."