Ruth Kelly, the Education Secretary, insisted that "protection of children" was her highest priority, after being criticised for allowing a man on the sex offender's register to teach sport in school.
She said officials were reviewing the case, "to see whether further changes are necessary" to the system that allowed Paul Reeve to be given a job at the Hewett School in Norwich last month, despite being cautioned for accessing banned images of children on the internet in 2003.
Ms Kelly said: "We will consider, for example, whether we can ensure greater correlation between the sex offenders' register and List 99. If further improvements are needed on the basis of advice received, I won't hesitate in making them."
Ms Kelly considered evidence that he had accessed paedophile websites inconclusive and so did not place him on List 99, the list of people barred from working in schools.
The National Confederation of Parent Teacher Associations had described the situation as "terrifying". Margaret Morrissey, an NCPTA spokeswoman, said: "Our big concern is that if there is a problem with the system, which there evidently is, then how many other people are slipping through the loophole?"
Police alerted the school's headteacher and Mr Reeve was stopped from teaching physical education after eight days at the school.
Tom Samain, the school's headteacher, and Marion Wright, the chairman of the governors, said in a statement about the teacher's removal: "We are concerned at the policy contradictions it throws up, and have raised our concerns with the DfES."
The National Union of Teachers general secretary Steve Sinnott said: "Children should not be put at risk. If somebody is on the sex offenders' register they should not be in school."
Jacqui Smith, the Schools minister, speaking on the BBC Radio 4 Today programme, stressed that the system stopped Mr Reeve from working as a teacher. "Let's be clear. This person isn't working as a teacher. The system broadly saw that that didn't happen," she said.Reuse content