The professional trial of a psychotherapist who agreed to try to change a homosexual man’s orientation has been suspended after allegations of attempts to intimidate a key witness.

Supporters of Lesley Pilkington, the Christian therapist who faces being struck off, called in police after they said an expert witness was threatened in several ‘menacing’ phone calls.

The witness was warned not to appear at the hearing, it was alleged.

The case is yet another controversy over Christian beliefs and the rights of Christians to hold to them at work.

Mrs Pilkington was targeted by a homosexual journalist who persuaded her to help him change his sexuality.

Patrick Strudwick attended sessions with her with a tape recorder strapped to his stomach and then published a critical article about her in The Independent newspaper.

She is now appearing before a professional conduct panel of the British Association for Counselling and Psychotherapy and faces losing her accreditation if she is found to have breached its rules.

The Christian Legal Centre, a group that is supporting Mrs Pilkington in the case, said yesterday: ‘Shortly before the hearing, BACP required all witness statements to be passed to them with contact details.

‘Immediately after supplying the statements, an expert witness received several menacing phone calls, threats and intimidation, telling the witness not to attend.’

The organisation has reported the alleged intimidation to police and called for a full investigation. A BACP official confirmed yesterday that the hearing was adjourned.

The ‘conversion’ therapy practised by Mrs Pilkington, 60, is held in contempt by homosexual lobby groups which normally support attempts to change sex but not the right to try and change sexual orientation.

Mr Strudwick runs a campaign called the Stop Conversion Therapy Taskforce, and has said: ‘Every major mental health organisation in Britain and America is opposed to attempts to change someone’s sexuality. There is good evidence not only that it doesn’t work but that it is harmful.’

However, in 2006, the homosexual rights activist Peter Tatchell wrote in the Guardian: ‘Much as I would love to go along with the fashionable “born gay” consensus (it would be very politically convenient), I can’t. The evidence does not support the idea that sexuality is a fixed biological given.’

Mrs Pilkington has treated ten patients over the past decade using a programme called Sexual Orientation Change Efforts. She says that her gay son is among those she has been able to help.

The psychotherapist has said that she was entrapped by Mr Strudwick, who she said approached her claiming he was depressed and needed therapy. She added that she had told him she worked within a Christian and Biblical framework and he had agreed to that.

Andrea Minichiello Williams, of the Christian Legal Centre, said yesterday: ‘Mrs Pilkington deserves to get a fair hearing by her professional body. In this case the homosexual lobby has been extremely militant and sought to silence by threats and intimidation.

‘The only professional, appropriate thing to do today is to adjourn the hearing and for the BACP panel to call in the police to investigate.’