A cross-party group of 15 MPs have sent a joint letter to Health Minister Norman Lamb calling on him to do more to address the problem of gay-to-straight conversion therapy.

The letter, initiated by MP Diana Johnson, Labour’s Shadow Home Office Minister for Crime and Security, demands the government take six measures to address the problem.

It urges ministers to investigate potential NHS links with conversion therapists, explore the regulation of counselling and psychotherapy, look into banning conversion therapy for under-18s and properly train mental professionals in LGBT-friendly forms of mental health provision.

The letter states: “Since 20 November, yet more evidence has emerged concerning the dangers of modern-day conversion therapy, with a report by BBC Newsbeat highlighting the plight of an anonymous young woman from West Yorkshire, treated for her sexuality in 2007. This adds to the already considerable evidence, both from academia and the press, that conversion therapy is a surprisingly prevalent problem in Britain today; and that it is part of a much broader issue of poor public service provision more generally for the LGBT population”.

A 2009 survey of 1,328 accredited mental health professionals showed 17% of practitioners readily admitted to having assisted at least one client to reduce their same-sex attraction.

Some 35% of patients therapists described were referred to them for treatment by general practitioners, and 40% were reported as actually being treated inside an NHS practice.

Signatories of the letter include MPs, Crispin Blunt, Hugh Bayley, Clive Betts, Sir Peter Bottomley, Geraint Davies, Stephen Gilbert, Mike Freer, Nia Griffith, Andrew Gwynne, Sharon Hodgson, Sandra Osborne, Andrew Percy, Iain Stewart and Mike Weatherley.

In November last year, the UK Government resisted calls by MPs to introduce statutory regulation of psychotherapists in order to prevent them from being able to carry out gay-to-straight conversion therapy.

Health Minister Norman Lamb said it was “utterly abhorrent” but that the Department of Health was not aware of cases of it being prescribed on the NHS.

The Liberal Democrat MP said: “We believe statutory regulation would not be appropriate and the costs to registrants or the taxpayer could not be justified.£

He added that “while statutory regulation is sometimes necessary it is not always the most proportionate or effective means of ensuring the safe and effective care of patients.”

Mr Lamb said the Department of Health was “not aware that the NHS commissions this type of therapy,” but added they were exploring ways to ensure that it did not take place in the future.

He said the government would instead press ahead with a new “voluntary register” for psychotherapists.

However, he admitted it would not prevent the practice from going ahead.

Labour MP Geraint Davies has published a Private Members’ Bill in Parliament aimed at banning the practice by regulating the psychotherapy sector.

The bill will receive its second reading in June.

In February, Stonewall and the UK Council for Psychotherapy released a joint statement against gay-to-straight conversion therapy.

It was prepared by the leading psychological professional bodies in the UK, at the request of the Department of Health.