The cult favoured by Hollywood stars is to pay £155,000 for harassing a woman in a six-year campaign of hate.
Bonnie Woods became the Church of Scientology's target when she left them and began counselling people who got caught up in religious sects.
Now the church, whose followers include Tom Cruise and John Travolta, has agreed to apologise in the High Court today for orchestrating the dirty tricks campaign against Mrs Woods.
It will promise not to repeat allegations against her, under the terms of the settlement of a libel action she brought against the church.
Mrs Woods, 49, from East Grinstead, Sussex, warned people about the controversial activities of the church, which was accused of brainwashing recruits and treating them like slaves.
In 1984 it was described as "corrupt, immoral, obnoxious, sinister and dangerous" by High Court judge Mr Justice Latey, who said its founder, L Ron Hubbard, was a charlatan.
The cult, which claims to have 100,000 members in Britain, described Mrs Woods as a "spreader of disinformation who has caused untold upset among families".
In 1993 the cult issued leaflets denouncing her and then had a private detective follow her. Demonstrators paraded outside the home she shared with her husband Richard.
Their house was watched and details of the couple's background were published in a Scientology newspaper distributed in East Grinstead.
The cult also gave free legal help to a woman creditor to sue Richard Woods four years after his building firm went bust. As a result, Bonnie Woods was declared bankrupt.
This morning, however, her nightmare will be over when lawyers for the cult will read out a statement in open court regretting its actions and agreeing to pay £55,000 damages and £100,000 costs.
Ian Thomas, a solicitor at the top London firm Allen and Overy said: "It means that the Church of Scientology won't be allowed to repeat these allegations without being in contempt of court."
* John Travolta is to star in a Hollywood movie version of Battleship Earth, a science fiction novel by Scientology founder L Ron Hubbard.