The loophole was revealed by The TES in 2002 when it reported that a teacher on List 99, following a conviction for importing indecent images of boys, was running a private tuition service in Sussex offering A-level and GCSE courses to children.

That man was Keith Hudson, who found himself at the centre of the scandal this week as it emerged that he had been cleared by the Department for Education and Skills to work in girls’ schools.

Last year a study by London university’s Institute of Education found that more than a quarter of 11 to 18-year-olds had had a private tutor at some point during their schooling. Even the Prime Minister has resorted to paying for private tuition for his children.

Myleen Curtis, the managing director of national agency, Fleet Tutors, ensures that all 2,400 tutors on her books have had full Criminal Record Bureau checks but wants to see the law tightened to make it mandatory. “It is an unregulated industry,” she said. “There needs to be change. One in four families in the UK has private tutors and these tutors work one to one privately with a child. I think it is a real gap.”

The Government does plan to make it easier for parents to make their own checks on home tutors with its new “vetting and barring system”.

The scheme would allow employers - including parents hiring home tutors or music teachers - to do a free instant online check on a job applicant.

This system will be updated continuously so employers such as schools or parents can re-check staff, rather than relying on a “snapshot” check which was only valid the day it was issued.

Legislation for the scheme is due to be included in a Safeguarding Children and Vulnerable Adults Bill this year, and the system is due to be phased in during 2007 and 2008. The DfES is also hoping to make it an offence for employers, including schools, to employ unsuitable individuals.