DEFIANT Ruth Kelly insisted today that she would not resign as Education Secretary.

As the row continued over the employment of sex offenders in schools, Ms Kelly vowed to make sure mistakes did not happen again. And in an exclusive interview with the Bolton Evening News, she said: "I am not going to go.

"I am determined to see through the changes that will stop this from being able to happen again.

"The protection of children is of the utmost importance."

Ms Kelly, MP for Bolton West, found herself embroiled in a political storm after it emerged her department had cleared PE teacher Paul Reeve to work at a school in Norwich last year even though he had received a police caution for accessing banned images of children on the internet.

He was able to work for eight days before leaving when police raised the alarm.

Last night, government minister Kim Howells admitted that it was he who cleared Reeve, who had been placed on the sex offenders' register, to work in the school.

He was Higher Education Minister at the time and he said he had acted in "good faith".

Ms Kelly has accepted full responsibility for her department's decision and promised in the Commons on Thursday to tighten the law on sex offenders.

She told the Bolton Evening News: "Child protection is a priority and it is vital that the public have confidence in schools.

"The department has been working for the past 18 months to introduce a new framework and draw up a Parliament Bill to tighten up measures, which have been in place for the past 80 years."

The MP said that the decision over Mr Reeve had occurred because the present law states that a police caution cannot be treated as a conviction and, therefore, the person involved could not be placed on List 99, the Education Department's own list of those barred from working in schools.

She said: "The new Bill will allow us to treat a caution as a conviction and allow us to bring together the sex offenders' list, which is held by the police, and List 99.

"I hope that this bill will get cross-party support. I will see these measures through."

Mr Howells worked as Higher Education Minister in the run-up to last year's General Election and he said last night that he had read Mr Reeve's file thoroughly.

He released a statement through the Foreign Office saying: "As duty minister for the Department for Education and Skills in the first days of May, 2005, it was my job to reach a decision on any cases put to me under long-standing arrangements followed by government ministers in both parties.

"I read Mr Paul Reeve's file very carefully and sought advice about the facts obtained in the file.

"They argued that this person did not represent an ongoing threat to children, but that he should be given a grave warning.

"I took that advice in good faith and acted accordingly.

"The decision that followed about whether he should be employed or not at a school was obviously a matter for his would-be employers with all the facts in front of them."

Mr Howells said he "fully supported" Ms Kelly's pledge to tighten the law on sex offenders.

Ms Kelly announced in the Commons an "exhaustive review" of the unknown number of cases in which ministers have cleared individuals on the sex offenders register to work with children.

And she said that in future, anyone cautioned for a specific offence would be treated the same as if they had been convicted and barred from working with children for life.

Following Mr Howells' statement, the Department for Education and Skills said: "Ruth Kelly takes full responsibility for all decisions taken in the department."

Earlier, Downing Street insisted that Ms Kelly had the Prime Minister's confidence. But MPs and children's campaigners continued to demand answers as the controversy refused to die down.

Children's Commissioner Professor Al Aynsley-Green said he was "extremely concerned" by the affair.

"At the end of the day, a parent has the right to know that when their child goes to school, they are going to be safe," he said.

Ms Kelly told MPs there had been a "small number" of similar cases where ministers had decided adults on the sex offenders register were fit to work in schools.

But she insisted that Britain had "some of the toughest sex offender laws in Europe".

The minister promised legislation in February to implement the recommendations of the Bichard Report into the Soham murders of schoolgirls Holly Wells and Jessica Chapman.

Sir Michael Bichard recommended that the vetting and barring system should treat individuals with cautions and convictions in the same way, said Ms Kelly.

"In future, where a conviction for a specified offence would have led to an automatic barring from working with children, a caution will also lead to an automatic barring from working with children," she said.

Shadow Education Secretary David Willetts branded her statement "extremely disappointing".

"The confidence of millions of parents in your judgment and the department you run is fast ebbing away," he told her in the Commons.

Channel 4 News reported that Mr Reeve had been given his job at the Hewett School in Norwich because Ms Kelly thought he was regarded as "trustworthy".

It said Mr Reeve had received a letter from the head of the Safeguarding Children Unit at the Department for Education on behalf of the Secretary of State.

The letter said the Secretary of State had "taken into particular account the supportive testimonials submitted on your behalf, which indicate that your teaching abilities were considered to be of a high standard, and that you were thought of as a trustworthy person".