Cruise, 42 — whose new film, War of the Worlds, had its London premiere last week — rounded on Matt Lauer, genial host of NBC’s Today programme, when the subject of their interview turned to the controversial religion and the prospect of his fiancée Katie Holmes, 26, being converted.

“Scientology is something that you don’t understand,” declared Cruise. “It is a religion. Because it’s dealing with the spirit. You as a spiritual being.”

The interview became more combative when he was asked about a public reprimand that he gave recently to Brooke Shields, the actress, for taking antidepressants rather than vitamins when she was diagnosed with postnatal depression.

Founded by L Ron Hubbard, the science fiction writer, in the 1950s, Scientology — which claims more than 8m members worldwide — teaches that psychiatry is “Nazi science” and that its medicines are all about mind control.

When Lauer said that many people had been helped by such drugs, Cruise dropped his famous smile and declared: “You are glib. You don’t know the history of psychiatry. I do.”

Although such pronouncements have raised Cruise’s profile in the run-up to the release of the £100m film, there are signs that they may encourage some people to stay away.

According to a poll published last Friday by the MSNBC TV channel, 69% of viewers said Cruise was “just plain wrong” on the role of doctors and the use of drugs to alleviate mental distress.

Some 61% of Entertainment Weekly magazine’s readers, meanwhile, said they did not like the new ebullient Cruise as much as the quietly controlled superstar of yesteryear. And 41% said they would not go to see his new film — as against 34% who said they would.

Until recently Cruise — who has reached the status in Scientology comparable with that of a senior Church of England figure privy to its inner secrets — followed the advice of Pat Kingsley, his veteran public relations adviser, to stay “engagingly mysterious” about his beliefs. Then Cruise sacked Kingsley and decided to start promoting his faith loudly.

Last week it was widely reported that when he was preparing to shoot Mission Impossible 3, due to start filming later this year, he tried — unsuccessfully — to convert his potential co-star Scarlett Johansson to Scientology.

On the War of the Worlds set Cruise paid for a “cappuccino tent” where crews could ask for an “assist” or interview, with Scientologists dishing out the coffee.

Cruise said that he felt “liberated” talking about such issues and dismissed scepticism about his three-month romance. In another part of the NBC interview he told Lauer: “I have never worried about what other people think and what other people say. I am really happy. I can’t restrain myself.”

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