Attendees at Emmanuel Centre, London, say ‘sexual orientation change efforts’ are necessary as Barack Obama and the NHS say practice is harmful and unethical

There was something of a siege mentality at the Emmanuel Centre in central London, the venue for a conference to promote “sexual orientation change efforts” – more commonly known, and derided, as gay conversion therapy.

Many of the sessions were closed to the press (to facilitate, we were told, open discussion in private). A day earlier, a Ukip parliamentary candidate pulled out of the conference after the media started asking questions about his presence. Barack Obama last week lent his support to a campaign calling for a federal ban on the practice. And in the UK, 14 health organisations, including NHS England and the Royal Colleges of GPs and Psychiatrists, have signed a memorandum of understanding stating that “efforts to try to change or alter sexual orientation through psychological therapies are unethical and potentially harmful”.

That view is not shared by those gathered at the Emmanuel Centre, who feel that it is not people’s sexuality that is under attack, but their religious and professional freedom.

In a hall with posters on the wall, declaring: “No anal sex in schools thanks,” and “Women make lousy Dads/Men make lousy Mums”, speakers took turns to berate the left, and to bemoan an increasingly secular society.

Mike Davidson, from the Core Issues Trust, the main organisation behind the Transformation Potential conference, said: “For me, it’s important to hold the flag up. It need be only a little flag but if there’s no flag it’s an erosion of freedom.”

John Nightingale, who described himself as a chairman of a counselling centre, put it in less allegorical terms.

“Our world view [as Christians] is given, if you like, a different categorisation from many others ... It seems on some subjects you are allowed to have disagreeing opinions ... but on others you’re not.” He likened treating “unwanted” same-sex attraction – the speakers were generally at pains to include the adjective “unwanted” – to people genetically disposed to depression. Another speaker described it as a “condition”.

The Core Issues Trust, which was joined by Christian Concern and Anglican Mainstream in organising the conference, is the same group that courted controversy by trying to run a poster advertising campaign on London buses – in opposition to one by Stonewall championing gay rights – stating “Not gay! Ex-gay, post-gay and proud. Get over it”. It was blocked by the mayor, Boris Johnson.

Dermot O’Callaghan, from the trust, offered advice on how to counter the argument that conversion therapy is harmful. “The decision [from others] is gay is good and therefore to try and change is bad, but you can’t say a married man’s desire to reduce his same-sex attraction is bad.”

Mainstream scientific and medical opinion has turned against gay conversion therapy – albeit only relatively recently. The campaigning journalist Patrick Strudwick subjected himself to conversation therapy in order to expose the practice, and eventually took a case against one of his therapists to the British Association for Counselling and Pyschotherapy, the largest professional body for counsellors in the UK, which found her guilty of malpractice. Since 2009, the American Psychological Association has asserted any attempt to change an individual’s sexual orientation is unethical.

But the “pray the gay away” movement – the remaining advocates of gay-cure therapy do so from an almost exclusively religious standpoint – continue to insist, in conferences such as this, that conversion therapy is legitimate.

O’Callaghan warned that if psychologists in Britain were prevented by legislation or other official policy from counselling people who wanted to end their attraction to members of the same sex, they would resort to the equivalent of “back-street abortionists”. He told the audience: “The new science is not science but ideology. The memorandum will increase rather than decrease the risk of harm.”

Gay rights groups say the continued existence of organisations such as Christian Concern and conferences such as the one that took place in London on Tuesday highlight the need for awareness to be raised about the issue. A Stonewall spokesman said: “A conference like this demonstrates that there is still a lot more for Stonewall to do. Sexuality is not something that can, or should, be cured. The only thing we’re hoping to cure is discrimination against lesbian, gay, bisexual and trans people in Britain and overseas.”

LGBT and human rights campaigner Peter Tatchell said: “The consensus among the world’s leading psychological and counselling organisations is that these therapies are unethical, ineffective and harmful. After two decades of practising ‘gay cure’ therapies in London, the Christian-based Courage Trust abandoned them. They concluded that it was not possible to cure same-sex attraction. They witnessed first-hand the trauma and misery this so-called treatment caused. Most of the gay men that Christian groups claim to have cured have been subsequently caught out in gay bars and saunas. Some of them have admitted it was a total failure and apologised for hoodwinking the public.”

Back at the Emmanuel Centre in London, proponents of ex-gay therapy were unmoved by the lack of scientific evidence to support their claims, and the mounting tide of opposition from professional bodies – and, gradually, the political classes.

Peter May, a retired MP, insisted that if an individual wanted to modify their sexual orientation, it was not in the least bit unethical for a professional practitioner to accede to that request. Indeed, it may even save their life, he insisted, omitting to mention the above-average suicide rates among LGBT youth. “It does young people no favour at all – President Obama please take note, especially when HIV rates are rising – when the orientation they experience is [deemed to be] fixed for life.”