The Rev Sun Myung Moon has a global credibility problem. He believes he is the Second Christ, with a unique hotline to God and a mission to unite Christianity and the world. But his home country, Korea, has never quite seen it like that, nor has America, his adopted country.

Despite billions of investment in the United States - including his buying a newspaper and subsidising it to the tune of $10 million a year - America doesn't love him in the way he thinks it should.

The 77-year-old Korean's solution - for he is running out of time - is to stage the Moonies' biggest mass wedding yet in the capital city of the world's last superpower. Today, 30,000 couples will assemble in Washington DC in front of "the True Parents", the Rev and Mrs Moon, to receive the Blessing.

Nine conferences are being held simultaneously - all tickets and accommodation thoughtfully supplied by the Rev Moon - to participate in the World Culture and Sports Festival. Singer Whitney Houston has been lined up, at a reported cost of $220,000. The overall price tag for this bonanza is $9 million.

Yet the Washington DC festival is only the epicentre of a global event, according to grandiose Moonie press releases, which claim that another 3.6 million people all over the world are lined up to receive the Blessing.

These press releases are out of date by the time they arrive. Such has been the enthusiasm for the Blessing that the number of couples is now running at nearly 29 million. In fact, they may be approaching, ahead of schedule, the 36 million targeted for the next Blessing after this one, suggests George Robertson, their London spokesman.

The Rev Moon and his followers have a fascination with numbers - large, incomprehensible sections of his speeches are dedicated to their significance (12 is a favourite.) Each Blessing must be 10 times bigger than the previous one, adding a zero to the total number of couples at the previous Blessing: 1995 was for 360,000 and so now we were supposed to be at 3.6 million.

With a little prodding, Robertson explains how the current figure of 29 million is arrived at - although he disarmingly admits you would have to be a superman to prove the figure. If you have signed a petition in the last year pledging commitment to the Moonies' four principles of loving family life - and as many as 30,000 in the UK have - then you have unwittingly become one of those making up the Moonies' make-believe statistics and are destined to receive the spiritual benefits of the Blessing.

Robertson, with a former Presbyterian Scot's earnestness, insists the huge figures are about the Rev Moon's unflagging commitment to the family, and the importance of supporting and nurturing this sacred institution at a time of unprecedented strain, and his desire to extend the spiritual benefits of the Blessing ceremony to the whole world.

That message appears particularly discredited in 1997. The future of the Unification Church - the great cult bogy of the 70s - has never looked so wobbly. While the Rev and Mrs Moon preside, in gowns and paper hats, over the festivities in Washington this week and marry thousands of people who have never met each other before - the Moons match up applicants from all over the world by their photographs, apparently using deep spiritual insight - their eldest son, Hyo Jin, is under several probation orders, most recently for drink-driving.

This was the much-loved son once destined to take on his father's mantle. But the drink-driving is the latest chapter in a saga of wife-beating, cocaine addiction, adultery and carrier-bags full of the hard-earned cash of devoted Moonie members which has shattered the image of the Moons and their 13 children as the True Family.

The story told to an American divorce court by Nansook, Hyo Jin's wife, of life in the Moon family has enthralled the media and, with her book due out next year, will continue to do so. Meanwhile Moonies all over the world can pore over the gory details on the Internet.

Moonies were still absorbing the significance of Hyo Jin's fall from grace when another son, Cochin, was revealed to be running a gun factory in the US which produced a particularly deadly weapon - easy to hide and easy to fire. The mission of the Rev Moon - whose businesses in Korea have always contributed to arms production - for world peace is looking distinctly implausible.

Given this kind of publicity, Moon appears to have adopted two approaches. The first is the Blessing in Washington, which perhaps will be the last, most spectacular attempt to woo and wow America.

The second is to prepare his retreat. Moon has always said that one country must embrace him and his message wholeheartedly for the Unification Church to survive. Korea and America have had their turn. Uruguay is the country now singled out by Moon for this great destiny. He has poured money into buying a hotel conference centre, a newspaper and a bank, and is basking in the warm welcome of a country desperate for investment.

But the biggest, and most intriguing, project in Uruguay is the New Hope Farm on the Uruguayan-Brazil border. Moon sees it as a re-creation of the Garden of Eden and is building a model community. Offering training in agricultural methods and eco-tourism, it has cost $20 million so far.

Back in London, a few of the dollars being lavished on Washington's Blessing and the Uruguayan paradise might not come amiss. The London centre is shabby and badly heated. Members reportedly work long hours for little or no pay and are beginning to feel they've been exploited.

According to two former members, the movement is falling apart in the UK. Only 40 people from there are travelling to Washington for the Blessing's unique spiritual experience, admits Robertson, who says that, with membership figures stagnant or declining for over a decade, the UK movement amounts to no more than 800 people. Those members who remain are increasingly ignoring the church hierarchy and going their own way.

Robertson points to the bumper Blessings of recent years, with their millions of beneficiaries, as one of the factors which have alienated members. Before, one had to prepare spiritually for years - sometimes a decade of celibacy and repeated fasting - before you were judged ready to receive the Blessing. Now, anyone can roll up.

Nor does this Blessing's multimillion budget go down well. Members have seen other expensive, high-profile events come and go with no lasting impact on establishing the church's credibility or advancing its cause of uniting all the world's Christians under Moon's leadership.

Robertson and Marsh attribute the mismanagement to a culture clash that has also led to the church's image problems in the West: the emphasis on obedience and loyalty to the Rev Moon, the secretiveness and the preoccupation with status - getting the backing of famous people and big prestigious events - all come out of the movement's Korean origins.

The bizarre practices which are part of Unification ritual - such as husbands and wives beating each other on the backside on their wedding night - can be traced back to Korea. One former member describes the Moonies as a combination of Korean shamanism and the febrile Pentecostalist revival movements which swept Korea in the 1940s.

But Robertson says the church is changing dramatically. The Internet has had a huge impact in the last five years in breaking up the secretive elite's control of information. It has also established a public forum within the church for debate for the first time. "Hallelujah, it is bringing a far greater degree of truth," he says.

The Internet has enabled him to keep in touch with a breakaway group of Moonie dissidents in Los Angeles. The half-dozen couples no longer recognise the authority of the Rev Moon, although they are devoted to the ideals of Unificationism. This may be the way for the future, says Robertson. He for one clearly sees the disintegration of the church in the West on the agenda.

Despite this remarkably candid criticism of the church, the faith of Robertson and Marsh - and of former members - in Moon as a man in direct communication with God is undimmed.

"My own personal path has been of such goodness and beauty I can't see that the mistakes represent the core of the movement. They are peripheral and God is still behind the church," Robertson says.

Marsh, who has spent some time in America and Korea, describes with awe meetings with Moon which start at 9 a.m. and continue until 1 a.m. the following day, with Moon barely stopping to take breath.

But the plausible reasonableness of Robertson is belied by the recent speeches of Moon which former members fear are becoming more and more bizarre. An extraordinary emphasis on sex has emerged which is shocking to the prudish Moonies, who have always placed great emphasis on sexual purity. Moon talks at length about the differences of "absolute sex" and "free sex". He discourses on how sexual organs fit together - in a recent speech he even analysed the significance of the Korean peninsula and its similarities to a penis.

In another speech last year, Moon launched an attack on the physiognomy of American women: their "high noses" represent "Satan's spear tip" while their large, deep-set eyes indicate the "hidden mind of thieves" and represent "Satan's warehouse". In the same speech he returned to an increasingly apocalyptic theme: "Unless America follows the Rev Moon it is bound to perish." He said he was offering America the pain of surgery to give it new life.

Some former members are worried. The more moderate elements are going their own way, leaving a dedicated core following an elderly Moon, who is embittered by his sense of rejection and increasingly erratic. There are dark rumours about Japan, the church's cash cow, buckling under the financial strain of funding Moon's extravaganzas, and there have been references to the oriental faithful moving en masse to Uruguay.

The new Eden beckons and no one is certain where what could be the Rev Moon's last bid for global spiritual leadership will lead.