The Church of Scientology, once described by a judge as "corrupt, sinister and dangerous," is under investigation by the Home Office for targeting drug-addicted prisoners.
The Home Secretary, David Blunkett, is considering banning leaflets used by the sect to recruit inmates to its anti-drug programme.
Prison groups and anti-cult campaigners fear that the organisation, whose members include the actors Tom Cruise and John Travolta, is trying to infiltrate British prisons. Bob Keenan, a spokesman for the L Ron Hubbard Foundation, which is part of the church, said the ads were "just to inform people." However, Harry Fletcher, from the National Association of Probation Officers, said the circulation of Church of Scientology literature to prisoners and people on probation was "extremely worrying."
The leaflets are being circulated by Criminon UK, the charity which runs the sect's drugs programme. It says it uses vitamins, minerals and saunas to sweat out toxins, thereby curing addicts. Criminon says it treats up to 200 prisoners a week.