Files from the National Archives at Kew include a confidential report produced by the then Department of Health and Social Security in 1977 for Home Secretary Merlyn Rees stating the church was a “considerable evil”.
It was written as the Government prepared to defend itself against a number of writs filed by the church relating to a 1968 statement announcing a ban on foreigners entering Britain to work or study at the church.
The document states: “The effect of losing the actions could of course be grave, not only for the defendants, but as giving some seal of respectability to an organisation which is essentially evil.”
Some of the evidence it would use in its defence against the writs is outlined in the document.
It includes an allegation that the church at its UK headquarters in East Grinstead took in English people with a history of mental illness.
The document says the young members paid fees of £450 and £500 before being classified as troublemakers and put out on the street after suffering breakdowns.
The document also talks of “vicious and barbaric” punishment for members who neglect their duties.
It says some were forced into menial jobs with no sleep for 48 hours with a 15-minute break every six hours.
Others have been imprisoned for 48 hours in a hatch too small to allow them to lie down or stand up.
The report also says that any person classified as an “enemy” was considered “fair game” by the church.
The document says such a person may be “deprived of his property by any means, be tricked or sued or lied to or destroyed”.
The report’s author urges the Home Secretary not to change the law regarding scientologists because it could weaken the Government’s case at the libel trials.
Elsewhere in the files another document says the church is “an organisation designed to make money, and perhaps also gain power”.
It says the church alienates young people from their families “obtaining large sums of money for its courses on the strength of wild claims that they can cure all sorts of physical and mental ills”.
The ban on foreign scientologists entering Britain was eventually lifted in the Eighties but the church is still not classed as a religion by the Charity Commission.
A spokesman for the church in the UK attacked the report, saying it was “an old document based on no evidence”.
He told the BBC: “The ban was lifted in 1981. Obviously these allegations were not true. If just a fraction of the outrageous allegations made about scientology were true, it would not be here today.”
Set up in the United States in 1954 the church, according to the files, started to spread to Britain in the Sixties.
It offers self-improvement on the basis of the writings of the late science-fiction author L Ron Hubbard, who spelled out principles that he called scientology and dianetics.
Critics have claimed it is a fake religion based on making money from its followers, who include film stars Tom Cruise and John Travolta.
He claims he was shouted at, spied on, chased and had his hotel invaded at midnight while making the programme.