Roy Grimshaw, who also uses Wilfred as a first name, met the personnel manager at the Guy's and Lewisham Trust yesterday morning and offered his resignation, according to the hospital.
This followed allegations in a Sunday newspaper that Mr Grimshaw had previously served two years of a six-year sentence for forgery, perjury and assault on women arising from his impersonation of a gynaecologist.
Health unions have demanded that the man should be prosecuted for deception, and Guy's said it was reviewing its appointment procedures. However, no legal action had yet been taken and a spokeswoman said she did not know if the police had been informed. She confirmed that references were taken up for Mr Grimshaw, but not from Chase Farm Hospital, in north London, his only other NHS appointment.
Earlier, Sky News reported that a man claiming to be Mr Grimshaw had contacted them and said he was resigning. The man said he had made no mention of his criminal past when applying for the job.
He told Sky: 'Because my prison past has come out, I think to save embarrassment to the hospital I will resign from the position forthwith. In fact I have already done that.'
Sky said the man denied falsifying references when applying to Guy's. But he told them: 'I made an ommission on any offences that I had committed in the past, that I had been in prison. But as it wasn't, as far as I was concerned, covered by the Rehabilitation of Offenders Act, I was under no obligation to inform them of that.'
According to Sunday's News of the World, Mr Grimshaw is obsessed with medicine, and opened a private gynaecology clinic in Lytham St Anne's, Lancashire, where he carried out 26 operations. He was jailed in 1983 on 11 counts. Three years after his release, he worked as a manager at Chase Farm Hospital, the newspaper claimed. On 15 July he was appointed to a new position at Guy's, beating 130 applicants.
He had used his middle name, Wilfred, and a bogus curriculum vitae, the newspaper said. He had 'bought' a doctorate from an American university and used it to give himself the title of doctor. A statement from Guy's yesterday said: 'This morning, the personnel manager for Guy's met with Wilfred Grimshaw who stated that he had resigned his post as clinical services manager and we are presently awaiting his letter of resignation. Wilfred Grimshaw has now been suspended from duty.'
A spokesman said Mr Grimshaw's job included business planning, budgeting and marketing for operating theatres, anaesthetics, intensive care units and radiology, as well as organising staff rotas in these departments. It was a managerial post, not a clinical one, and Mr Grimshaw had not been responsible for the work of doctors. 'No patient was at any risk whatsoever,' he said.
The hospital said the police had been informed of the affair.