AS congregations in the Church of England collapse to an all-time low, the Mormons - officially known as Church of Jesus Christ of Latter- Day Saints, appear to be going forth and multiplying far more effectively. The number of practising Mormons in Britain has risen from 6,500 in the mid-Fifties to 180,000 today. Worldwide membership of the church has topped the 10 million mark.

The Mormon church was founded in 1830 in New York State. Missionaries came to Britain in 1837 and preached their first sermon in Preston, Lancashire and it was only in the late 1840s that they trekked to Salt Lake Valley in Utah, now the church's international headquarters. Mormons place a big emphasis on missionary work - nearly 1,600 missionaries serve in Britain - and on the family as a basic unit of society. Family relationships, they believe, continue into eternity.

Now Preston is the focus again. Next Sunday, 7 June, the Latter-Day Saints, as they prefer to be called, will dedicate their second largest temple in the world. Not in Utah, but in Chorley, just outside Preston. For the past two weeks, it has been open house at the new temple. More than 100,000 visitors stepped inside before it was closed forever to the uninitiated. About half were paid-up members of the Mormon church (no pun intended, but members pay ten per cent of their income to the church.)

Among the visitors were American descendants of the first missionaries. The rest of the visitors had come out of curiosity, to feast their eyes on the interior of a building which is rumoured to have cost between pounds 50m and pounds 100m.

"The baptismal font will blow your socks off, I promise you. There's been nothing like it since the Temple of Solomon," promised Bryan Grant, who became a Mormon 30 years ago after a missionary knocked on his door.

The 35-carat gold trumpeting angel at the top of the temple's steeple can be seen from miles around. The building itself bears down on motorists whizzing along the M61 below, a testament to the growth of the church, particularly locally.

"The church in Chorley has doubled in the last year," said Mr Gould, now the church's director of public affairs. "There are 280 worshippers each Sunday. They're going to have to divide the ward into two congregations. Over the last quarter of a century we have opened a new congregation somewhere in Britain every two to three weeks, and a new chapel every six weeks."

It is rare for a state or country to have more than one Mormon temple. But the temple in Preston is the UK's second (the first is at Lingfield in Surrey).

Regular Anglican church attendance has diminished by more than half in 50 years - dipping below 1 million for the first time in 1996. "The churches feel a little bit threatened by the success of the Mormons and so like to perpetuate the stereotypes," said Mr Gould. "People like to think we've been here 10 minutes and we're all Americans."

Don't you believe it. There was an abundance of Mormons with British accents in the queue last week. Take, for example, Margaret Bridges, a 47-year-old civil servant from Bristol, who converted seven months ago. "Three weeks after I found out about the church I joined, and three weeks after that I was baptised. It was the best move I've ever made," she enthused. "I just knew I had to join. I went in, saying my first prayer and singing my first hymn, and thought: 'I've got to do this'."

Ms Bridges was brought up in the Church of England, but never felt inclined to pursue that faith. "The Mormon church is not so much a church as a way of life," she said. "It's not something you do for an hour on a Sunday. You get up with it on Monday morning and go to bed with it on Sunday night."

Since becoming a Mormon, Ms Bridges has felt much calmer. "Everybody looks after each other," she said. "You all live by the same rules so you know this lady [pointing to the woman standing next to her] will be doing exactly what I'm doing."

Mormons are law-abiding citizens, who follow a health code which forbids stimulants such as tea, coffee, alcohol, harmful drugs and tobacco. They attend weekly services on Sundays in a chapel, also the venue for other religious activities. Their temples are reserved for special ceremonies. It is here that family members are "sealed together", not just for this life but for "time and eternity". It is also where they perform baptisms, saving their ancestors retrospectively.

Heather Fell, 47, from Scunthorpe, had come for the day with her children and grandchildren. "I think it's the way the family lives," she said. "Families are very important because, to us, we're going to be with them for eternity."

Some visitors, like Philippa Dunn, 16, from Blackburn, emerged none the wiser. "All I knew is that they wear suits and are American, and I don't know much more now," she said. "It's more like a hotel than a church. All those chandeliers. It's not really religious. The way you look around, it's like a stately home."

Helen Sadler, 17, took the day off college to visit the temple with her Mormon boyfriend, Craig Collier, 19, a funeral director, whom she met a year ago. Whenever she accompanies Craig to church she says, she feels that: "I want to be a part of this. I want some of that goodness."

The tour of the temple, not least the lavish Bride's Room, impressed her. "Magnificent is an understatement," she said. "It really brings home to you that the most important thing is your family and home and the love you have there." Craig was keen to point out that, should they get married, Helen would be his only wife. Many people think that Mormons are polygamous, but the practice was brought to an end in 1890.

Mr Gould believes the reason that the Mormon faith is expanding is "all about families" - the conventional, nuclear ones, that is. Monday evenings are set aside worldwide for "family home" evenings.

Couples have their marriage vows "extended for eternity" in the "Sealing Room" One of 150 rooms in the temple, it has multiple mirrors to "give the feeling of eternity". "This to me is the pinnacle of the temple," explained Mr Gould. "It's a family factory, where families are made."

The fabled baptismal font is in the basement, to symbolise death and rebirth. With changing rooms, lockers, tiled floors and marble surfaces, the area is reminiscent of an upmarket health spa. The font rests on the backs of 12 marble oxen, symbolically representing the 12 tribes of Israel. Here Mormons perform baptisms on behalf of their ancestors. "We admit we don't know whether our great, great grandfather wants to be baptised," said Mr Gould, "but we do it as a labour of love."

Mr Gould spoke with pride of the materials: the American cherry wood, the crystal chandeliers from Austria, the font from Germany, the crushed marble from Spain, the granite from Sardinia. "The Lord has commanded only the best of materials," he said, pre-empting the next question by adding: "Over the last 15 years the Church has given pounds 100m to the Third World."

Besides baptismal work and sealings, there is "endowment". A session lasts two hours and includes instruction on "the three great questions of life" - where did I come from? why am I here? where am I going?

Armed with the answers, the Mormons proceed from the Endowment Room to the Celestial Room where they can "ponder the purpose of life" in an ambience designed to give a feeling of "going into the presence of God". This requires a 300kg chandelier, a plush honey-coloured carpet, lemon yellow leather, and artificial pale pink roses adorning the side tables. Silence prevails.

James Beckford, Professor of Sociology at the University of Warwick, who has made specialised studies of religious movements and the public's reaction to them, believes that the combination of efficient marketing and its emphasis on family life accounts for the growth of Mormonism.

"Someone coming cold to the Mormon religion is offered a ready-made, friendly, community atmosphere where they can simply slot in and everyone shakes their hand and is nice to them. It's seductive and some people respond well to that very direct marketing approach. I think Mormon evangelists do what people who have taken courses in salesmanship and marketing do. But that is not say they are not doing it sincerely.

"It is the kind of religion in which all members of the family are expected to participate. It's an all-purpose community.Mormons like to have sing- songs around the piano. They do all the things that, if you read the community studies of British village life in the pre-war period, we used to do."

Asked whether the world was soon going to be taken over by Mormons, Mr Grant replied swiftly: "2036. We've worked it out. Well, that's if we continue at this rate."