Trusts are paying surgeons up to 900 for a half-day's work in a bid to clear waiting lists, it emerged this week.
The figure is more than 10 times the sum doctors could expect to earn for an NHS session.
The payments - condemned by doctors' leaders as 'market forces gone mad' - are being used to bring surgeons into NHS hospitals at weekends, or to buy places on private lists.
But one trust defended the level of payments and argued that it needed to buy space on private lists because it did not have the capacity to meet waiting list targets.
Hospital Consultants and Specialists Association chief executive Stephen Charkham told HSJ that one trust was also 'threatening' surgeons who refused to take on weekend work to help it deliver its waiting list target.
Association members had reported cases where trusts were willing to pay 'two, three or even 10 times the going rate'.
But he said the organisation had advised its members not to do the work if they felt it would compromise quality standards.
'Everyone needs some time off,' he said.
Keith Walker, planning director for Royal Bournemouth and Christchurch Hospitals trust, said it had been allocated 2m to deal with waiting lists and, lacking the capacity to do the work itself, had gone to the private sector.
Asked whether the trust was spending 900 a time on sessions, he said: 'I would think that is probably realistic for a private sector list. It is a realistic private sector rate.
'The point is that it is enabling NHS patients to benefit from additional capacity. These guys would be doing these private lists anyway, so other people would buy into that if we didn't.'
Mr Walker said the trust was advertising for consultants and theatre staff.
'When these staff arrive, obviously we will increase our NHS capacity and use the money to support that.'
Mr Charkham cited the case of 'a trust in the North of England', which he said was warning doctors a Department of Health 'hit squad' would be called in to inspect their NHS and private work unless they co-operated.
He said he had received one letter complaining: 'While it is entirely voluntary, it has been suggested that if we do not reduce waiting lists, we could each face a personal audit of our waiting lists and an investigation of our clinical practice.'
Conservative front bench health spokesman Philip Hammond, who raised the issue in a letter to health minister Alan Milburn, said the waiting list initiative distorted clinical priorities and wasted resources.
He said: 'I am not seeking to make a point about whether we did it right in the past, but we are concerned that this government made a promise about waiting lists before the election and won't now say 'we made a mistake'.'