In the long term, the charity wants to work with secular groups to help sex addicts such as chronic masturbators or heavy users of hardcore pornography.

'We're trying to get in to speak at youth conferences', said Lisa Guinness, the charity's smiley, silver-haired director. 'We'd love to take our stuff out to non-Christians, so we're going to develop some materials which could do that.'

The prospect alarms gay rights campaigner Peter Tatchell: 'They are preying on emotionally vulnerable young gays and lesbians. It would be irresponsible and dangerous for any school or youth organisation to have anything to do with them.'

Guinness is prepared for the uproar that will follow any attempt to take their controversial message to young people. 'There will be a backlash soon,' she said. 'We need to present what the consequence of this sort of behaviour is - infertility, sexually transmitted diseases, the breakdown of family life, fatherless ness for the next generation ... '

Living Waters offers its services to Christians at weekend conferences and evening classes over a period of up to 30 weeks. Groups of around five are each overseen by two leaders, usually people who have already attended Living Waters programmes. Around a third of those who attend are 'dealing with a gay struggle', said Guinness. A further third have been abused and the rest are dealing with problems ranging from low self-esteem to self-harm.

Central to the charity's philosophy is a belief that God can fulfil the father-figure role that Guinness claims is absent in most gay lives. 'The huge thing we focus on is God being our father - because most people are fatherless. With guys with a homosexual struggle, a lot of it is an eroticised need for a father, to be kind of covered and blessed.

'If you've got legitimate unmet needs when you go through puberty, they will become eroticised and they feel like they've taken on a life of their own, as if that's the sum total of who you are.'

A few months after the course, people notice the changes, said Guinness. 'Guys will say things like "I never realised women looked like that". It's a gradual thing, but over time it's totally life-changing.'

A former doctor who specialised in psychiatry, Guinness doesn't seem the sort of person who spends her time worrying about people's sexuality and whether it is compatible with the Bible. A vicar's wife with three children, she could pass for a headmistress. But in spite of her mild manner, Guinness has a tough shell. Those who fear Living Waters miss the point, she said. 'One of our core values is choice. If Christians are not happy with how they deal with their relationships or gender identity, they should be free to look at it in a Christian context. We're here for them. The liberal wing feel we are singularly unhelpful and shouldn't be allowed to exist. Conservative evangelicals don't know what to do with us either.'

The charity, the only one of its kind in Britain, is part of a growing pan-European operation with offices in 13 countries. The network was spawned from Desert Stream, the US organisation formed in 1980 by Andy Comiskey, a former homosexual who is now married with four children.

Desert Stream says its mission is based on 'confidence that Jesus Christ is the only hope for a world struggling under the weight of sexual and relational brokenness and the resulting destruction'. Such claims have come to the fore as the Anglican and Catholic churches have wrestled with the issue of homosexuality.

The conservatives in the debate hold that the Bible is unequivocal in its condemnation of homosexuality, but few religious groups go as far as Living Waters in claiming that people can have their sexuality 'rewired' through prayer and psychology.

But it is a claim that concerns Jeremy Marks, founder of the Courage ministry which helps Christians to come to terms with their sexuality. 'I've been working in this area for 18 years and no longer can support the idea of people trying to change their basic orientation. As far as I can see, it's pretty fixed in all of us,' said Marks.

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