A businessman is suing the Church of Scientology for hundreds of thousands of pounds, claiming that he lost his girlfriend and business after she became indoctrinated by the controversial self-styled church.

David Craig, who at one time joined the Scientologists, claims that he was persuaded to pay out more than £170,000 to the "spiritual cult" after his partner, Irina Glaser, was recruited by Scientologists. When, however, Mr Craig threatened to fight for custody of their infant son, he claims that Scientologists told him he would be expelled if he did not use their own judicial system to determine the case. The Scientologists did not wish to use what they referred to as "wog courts" (a derogatory term for the mainstream legal system), according to court documents seen by The Independent on Sunday.

The 48-year-old, from Lyndhurst, Hampshire, eventually left the church in 2004, according to court papers. Now his impending High Court case threatens to expose the inner workings of the notoriously secretive organisation. Last week an Australian senator labelled Scientology a "criminal organisation", and Prime Minister Kevin Rudd hinted at his support for an inquiry into the organisation when he said: "I share some of those concerns."

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In France, Scientology is currently embroiled in a landmark case where it has been accused of ruining lives and illegally prescribing drugs. The German government has recently moved to ban the organisation.

Founded by the science fiction writer L Ron Hubbard in 1954, Scientology now claims millions of supporters across the world, with the Hollywood stars Tom Cruise and John Travolta among famous devotees. Scientologists, who believe humans are descended from a race of aliens, claim that they can purify the human mind through a process called "auditing" or counselling.

Mr Craig claims that Ms Glaser joined the Scientologists after she attended a psychic fair in December 1999. Ms Glaser, who allegedly had "mental health issues", was attracted by the organisation's claim that it could cure all mental illnesses and that conventional psychiatry did not work. For several days afterwards the pair were allegedly "inundated" with calls from the Scientology mission in Poole, Dorset, in order to "encourage them to join the cult". In January 2000 the couple attended the mission and, after a "personal efficiency test", were told that auditing would rid Ms Glaser of her illness. She then "followed their advice and instruction", giving up her medication and undertaking a series of expensive courses. During 2001 she "immersed" herself in the organisation, eventually joining the staff at its East Grinstead headquarters in Sussex. She cut off almost anyone she was unable to persuade to join the church.

Mr Craig says he was "persuaded to give substantial sums of money to the cult" during 2001 and 2002 for Ms Glaser's treatment, his own auditing and the "work of the cult". But when he became "more concerned about the conduct of Irina Glaser" he told Scientologists at the Poole mission that he was prepared to go to court to fight for custody of their six-year-old son. Mr Craig was told by the Scientologists that he should use "the cult's own 'court'", the claim states.

After leaving the church in 2004, Mr Craig was told that he was expelled from the organisation because he had involved it in court hearings about his son. It is understood the boy now lives with his father. Mr Craig, who declined to comment, is claiming compensation for the loss of earnings and also the loss of his business. The church had told him not to challenge the loss of his business franchises in 2002, which he claims were worth £750,000. He is also claiming for legal fees.

The businessman claims that while he was "under the actual undue influence" of the church he also paid out £170,000 in fees and donations. Although £30,000 of this was repaid by the church, according to the court papers, he is now demanding the balance of £140,000.

Ms Glaser is believed to be a member of the church still. No date has yet been set for the full hearing. Mr Craig's solicitor, Clare Kirby, declined to comment.

A Church of Scientology spokeswoman said yesterday: "It is a nuisance, because it attempts to reopen something which was fully resolved in 2007. As far as we are concerned, it is in breach of the agreement Mr Craig made then. At a time when our church is enjoying unprecedented growth it is not unexpected that some disgruntled or self-serving individuals might seek to profit from our expansion, or for other reasons try to cause disruption."