Dr Paul Miller, a consultant psychiatrist and senior health advisor to Mrs Robinson, said he was working with a "small number" of gay people who were trying to become straight.

Dr Miller – who is a former member of the Royal College of Psychiatrists' Board and is an honorary clinical lecturer at Queen's University Belfast – claimed that he had seen hundreds of homosexual people become heterosexual.

"It is possible – I know these people and I've seen the outcome of the work in their lives so to say that it's not possible is simply not true," he said.

But last night the Royal College of Psychiatrists rejected Dr Miller's claim and said that it was not possible to change a person's sexual orientation.

Dr Miller, who is a former member of the Northern Ireland Association for Mental Health, was thrust into the limelight yesterday after comments by Mrs Robinson, who is the DUP chair of the Assembly's health committee.

She condemned a homophobic attack on a young man in Co Antrim, in which he was left for dead, but described homosexuality as an "abomination".

Speaking to the News Letter, Dr Miller said he had started his work trying to help homosexuals become heterosexual after a patient struggling with his sexuality committed suicide.

"One of the things that kept coming up was people who had a conflict between their religious identity and their sexual identity," he said.

"They were being told 'you are gay and you need to embrace that' but they were not happy with that and I had a very sad case of a man – who I was treating for something else, who took his own life.

"I don't want to be in a position again where I lose someone because they have been told something that is factually inaccurate, change is extremely difficult but it is not impossible.

"A lot of the research has never been disproven but it has become politically unacceptable to talk about it."

Dr Miller works both at the Mater Hospital, where he specialises in working with Alzheimer's patients, and in private practice where he specialises in working with trauma patients.

"I've been more focused on taking (sexual reorientation) cases on in the past two years," he said.

"Before, if it came up as an issue I'd have worked with people on it.?

Asked how he went about changing a gay person's sexuality, Dr Miller said: "The sexual behaviour stems out of a person's past, sexuality is complex and involves an interaction between genetics and the environmental background.

"I don't just work to change behaviour.

"What I do is I take a detailed history and I look at key relationships and their past and that would be relationships with mother and father and with peers, both same-sex and opposite sex peers.

"What I'm seeking to do is to help the person think as clearly as possible so that they can make as informed a decision as possible.

Dr Miller said that if a homosexual person worked through his course and decided they wanted to be "gay-identified to the world" that it was fine and he would not seek to stop them.

"But really the work I'm focussing on is for the people out there who say that they don't want to do that that they want to change that," he said.

Dr Miller said three key messages summed up his work.

"First, no one is born gay because gay identity is a complex interaction between genetics and environment; second, no one chooses to experience who they are sexually attracted to; and thirdly, change in sexual orientation is possible."

Dr Miller cited a study by American psychiatrists Stanton Jones and Mark Yarhouse which he said concluded that people can change sexual orientation and that the process of change was not damaging.

"That was a very robust study because in the past, and rightly so, people who worked in this field were criticised for not having robust research."

Dr Miller, who is a Christian, said that he had worked alongside Mormons, Jews and Muslims and added: "It's not a spiritual approach it's a psychological approach."

And he added: "As a therapist, I have to say that it's like anything there are some people who engage in therapy and they just find the change process too difficult.

"I think we have to look at ways of supporting people if that is the case which is why I think that within the churches we have to be more gracious in regards to people because it isn't a choice.?

But Dr Phillip McGarry from the Royal College of Psychiatrists said: "People are born with sexual preference - that is a fact of life.

"Treatments that purport to change someone's sexuality can be harmful and there is no evidence that they can be successful."

Last night a spokesman for NIAMH said: "The Northern Ireland Association for Mental Health is committed to improving the mental health and well being of every citizen in Northern Ireland and does not support discrimination or prejudice based on race, religion, gender or sexual orientation. The Association believes that every person has the right to chose where and how they get emotional and psychological support, personally or professionally."

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