And while many unorthodox movements are respectable, or at least long- established, there is increasing concern about shadier cults taking advantage of the young and vulnerable.
An estimated 16,000 religious movements have sprung up in the West since the Sixties. And, says Graham Baldwin, a former university chaplain who runs the anti-cult counselling group Catalyst: "Unless the Church gets its act together, Christianity will be finished in this country. There has been a tremendous sea change in religious attitudes, yet few people seem to have grasped it".
The size of the groups varies enormously. Among the more established movements, Scientologists claim to have 150,000 members, Mormons 170,000 and the Jehovah's Witnesses 130,000; surprisingly, the Moonies - or the Unification Church, as they prefer to be called - claim only 350 core members, but 30 churches.
And ever since the Beatles met the Maharishi, there has been a vogue for Eastern religions; Koo Stark, Clothes Show presenter Jeff Banks and his former wife, singer Sandie Shaw, are all Buddhists, while chanting PR legend Lynne Franks has been famously parodied by Absolutely Fabulous.
But there are also hundreds of thousands practising some kind of New Age faith, many drawing on a heady mixture of Eastern thought, paganism and science fiction. Among more bizarre are the Gnostics, an outfit promoting sexual magic, who believe in "internalising" orgasms for spiritual power. Elsewhere, an anti- Semitic cult is trying to raise a mercenary army to find the treasure of the Knights Templar in Cyprus.
A succession of headline horrors such as the Branch Davidian shoot-out at Waco, Aum Shinri Kyo's gassing of the Tokyo underground and the 39- member suicide pact of Heaven's Gate, has fuelled an impression that all such cults are hotbeds of sex, drugs and gun abuse.
While that is, presumably, rare, many worry about their predatory nature. "These recruiters are very crafty. For example, they often stand outside cinemas when people have seen a spooky film," says Fr Vladimir Felzmann, a Catholic priest who works with young people. "If you are vulnerable and need clear leadership, then they are there for you. Young people look for some identity and role."
Mr Baldwin identifies a certain type as attracted to cults. "They tend to be intelligent and well-educated. Most are in a transitional stage. Perhaps university has put them off balance, or they have lost their job or had a relationship break up. They are not screwballs, but are facing an unbalanced moment in their life." As for the cults: "It is about power. The power that people have over other people is very seductive."
Harry Coney, from the cult information group Inform, sees a strong common thread running through them. "Apart from a strong, charismatic leadership, their thinking is very dualistic:Right and Wrong, Godly and Satanic. Members are discouraged from having outside contact and encouraged to marry and keep social relations within the group".
Behind the cult explosion are a number of factors: the decline of traditional churches, the way people look at how science has changed the world and the growth of information technology, which has allowed ideas from all over the world to be available to anyone looking for answers.
Cult members remain unrepentant. "We are not trying to convert the nation, just trying to make it more spiritual," says Moonie George Robertson. "If you are Jewish, become a good Jew. If you are a Catholic, then become the best Catholic. That is the message we try to put across."Reuse content