Ruth Kelly's Education Department was warned of flaws in vetting procedures before it was revealed that sex offenders were working in schools, a leaked document showed.
Ms Kelly, MP for Bolton West, has faced furious criticism after it emerged that a series of people listed on the Sex Offenders Register had been cleared to teach since she became Education Secretary.
An internal policy briefing circulated in the department identified faults with the vetting system, The Guardian says.
Inconsistencies between lists - such as the Register and List 99, which covers teachers - were highlighted in the briefing circulated before Christmas, the newspaper says.
The briefing came to light as officials are working around the clock to prepare a statement by Ms Kelly to MPs on Thursday.
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