A therapist who claims he can help banish homosexual feelings has accused the therapeutic industry of "acting like 13th century priests" by ostracising him for his treatment.

Dr Mike Davidson became the poster boy of so-called "conversion therapy" last year – and public enemy number one for its many critics, after his group, the Core Issues Trust, mounted a poster campaign on buses, featuring the slogan "Not Gay! Ex-Gay, Post-Gay and Proud. Get over it!"

Uproar ensued and London mayor Boris Johnson banned the adverts amid claims that the campaign was homophobic and caused offence.

The opprobrium really started falling down upon Davidson's head when he went on BBC News to defend his campaign and the practice. Soon after appearing on TV screens, Davidson was suspended by the British Psychodrama Association (BPA) and cast firmly into the outer darkness of his profession.

He has remained there ever since - along with gay-to-straight talking therapy, which is condemned as a danger to vulnerable individuals for pathologising sexuality.

Core Issues Trust poster which was banned from London buses
Core Issues Trust poster which was banned from London buses

From this sequence of events it is easy to imagine a ranting religious zealot – condemned as a bigot by his own condemnatory views and doomed to practice quack therapy far away from polite society.

But Davidson in person is not like this.

During our meeting he was measured and almost diffident in manner, speaking with clarity and poise on the issue, which was only disrupted when his frustration welled up about the professionial pounding meted out to him. He denies his treatment pathologises sexual feelings.

"It's just hard," he said of the industry consensus against him and conversion therapy.

"The problem is we are not allowed to research this area. Which ethics committee in the UK will seriously consider human studies on sexuality involving this kind of thing? Unless it comes from a specific point of view it is not treated seriously."

Davidson's position begins from a belief that sexuality is fluid and liable to oscillate during a lifetime. He felt same-sex attraction when younger but has been married for more than 30 years. His personal Christian faith means that he sees same-sex feelings as potentially damaging for the likes of married men with children because it carries the possibility of divorce. This is anathema to many people – including many of his influential peers.

But he was adamant: "This is an educative issue, as I see it. I'm concerned with teaching people about these issues around sexuality and fluidity. This is not only for the hard scientists - the social scientists have got a contribution in all of this. I've got a place. The problem is anybody who doesn't think the way determined by professional mental health bodies, cannot progress."

Not viewing homosexuality as an equal equivalent to heterosexuality carries a hefty whiff of discrimination, which makes his therapy so unpalatable to many. Among them is Geraint Davies MP. The Labour politician is bringing a private member's bill which would make it illegal to provide 'gay-to-straight' therapies.

According to Davies, conversion therapy is prevalent in Britain to a surprising degree. Speaking to IBTimes UK this week, Davies claimed it was practiced by a significant minority of psychotherapists in Britain - one in six last year, he said.

"People who may be feeling confused about their feelings may find themselves in the hands of someone with an agenda of imposing their worldview," he said.

Needless to say, Davidson rejects this opposition and claimed that banning conversion therapy would end up hurting clients – exactly what critics say his therapy is doing right now.

Davidson denied he offers a 'gay cure.'

"Gay cure means you are saying there's some kind of disease that you are diagnosing and then offering a prescription to sort it out. Gay cure and reparative therapy are pejoratives.

"There's no disease around this - there are plenty of diseases which can arise from it, but I don't see it as curing people. I see it as supporting clients in an aspiration to explore possibilities and in some cases working it out with them. What in any type of psychotherapy are you not fixing when you practise it?"

Railing against the mainstream, he continued: "This is the promotion of one point of view: that you're born gay, there's nothing you can do about it. They act like a bunch of 13th century priests – 'We said it, you believe it, off you go'.

"How the tables have turned. This is a dogma. We know how Stalinism works. It removes any dissenting voice and they present their position as fact. This is very bad for a society that's meant to be about critique," he said.

Rejecting efforts to ban conversion therapy, he said: "It's self-defeating, as all you will have is back street practitioners. In the US, you can be a member of the American Psychiatric Association and practise this, while having your culture wars about it.

"They have the space to fight their case. Yet I got chucked out of the BPA for sticking my head above the parapet because they will not entertain the arguments."

A 46-page document Davidson wrote in his defence following his suspension was ignored by the BPA, he said. When contacted by IBTimes UK, the organisation refused several requests to comment on Davidson's claims.

Dismissing conversion therapy, the UK Council of Psychotherapy said: "UKCP does not consider homosexuality or bisexuality, or transsexual and transgendered states to be pathologies, mental disorders or indicative of developmental arrest. These are not symptoms to be treated by psychotherapists in the sense of attempting to change or remove them.

"It follows that no responsible psychotherapist will attempt to 'convert' a client from homosexuality to heterosexuality."

In comments unlikely to help him win over the ranks of conversion therapy's critics, he compared them to those in African countries such as Nigeria currently hounding homosexuals with repressive legislation.

Davidson said: "There's a complete closedown of critique in Britain and we have imbibed the doctrine that you are 'born gay.' If that can happen than I see how traditional cultures come to accept uncritically that homosexuallity is intrinsically evil. It's two sides of the same coin."

Davidson and conversion therapy look set to remain firmly on the fringes for some time yet.