Health minister Norman Lamb has written to NHS England calling for reassurances that GPs are not referring gay and lesbian people to controversial practitioners who say they can “cure” people of homosexuality.

Mr Lamb told the Guardian that gay conversion was based on a “false premise” that there is something wrong with the patient if they are gay. “I certainly want to do what I can, as a Liberal Democrat, to eradicate this,” he said.

He said that such referrals should not be made to NHS professionals. Mr Lamb said he had seen no evidence of any referrals, but added that in a “vast system” like the health service, “one imagines that could happen”. He reiterated that this would be totally inappropriate.

A third of mental health professionals said that a patient had been referred to them by GPs for such a cure in a survey in 2009.

Mr Lamb added that a “clear signal” had to be sent that NHS health professionals would be “entirely wrong” to make these referrals. But Mr Lamb stopped short of calling for a ban, saying some patients might wish to have treatment to come to terms with their sexuality. As well as this, mental health professionals would not wish to be in a legally difficult position.

Labour MP Sandra Osborne called conversion therapy a “very real and present danger” in the UK, and not an issue confined to religious fundamentalists - “it’s an issue for the NHS and professional sector”.