Some consultants are making more than £100,000 a year in overtime payments from the NHS, the BBC has learnt.
The sums - paid on top of basic salaries and bonuses - have been criticised at a time when the health service is trying to save money.
Consultants have been accused of playing the system, but doctors said poor planning by managers was to blame.
Overtime rates vary, but are often about £600 for four hours - treble what senior medics get for contracted work.
Basic pay for consultants stands at just under £90,000 a year on average. For full-time consultants, this pays for 10 separate four-hour blocks a week.
Consultants who do private work are also obliged to do an extra four-hour session paid at their basic rate if their NHS trust needs them.
Any extra work beyond that is then done at a higher rate under a system known as waiting list initiative payments (WLIs).
These are negotiated individually by each trust so there are no figures for how much is spent nationally.
The Department of Health stressed the need for the efficient use of money in the current climate.
However, the BBC has learnt that many trusts pay between £500 and £700 for the four-hour sessions.
Depending on what speciality they are in, consultants can earn tens of thousands of pounds on top of their basic pay.
Figures seen by the BBC show that, in some cases, consultants are making more than £100,000 a year.
Consultants involved in common forms of surgery, such as ear, nose and throat and hip and knees, tend to do the most overtime alongside anaesthetists. Others, working in areas such as geriatrics, are likely to get very little.
At Coventry and Warwickshire NHS Trust, one ear, nose and throat specialist made more than £105,000 in 2009-2010 in overtime. Another three consultants from other areas made in excess of £80,000.
Similar figures were also seen in the previous years.
Ed Burns, from Newton Europe, a consultancy which has carried out work for NHS trusts to improve productivity, said figures in excess of £60,000, including those above £100,000, would not be seen in every trust but were "not unusual" either.
He said poor job planning was the most common cause of high overtime payments, but added sometimes consultants fought against giving them up by employing tactics such as under-booking theatre sessions to make sure there was a need for overtime.
"Consultants work hard to provide the best possible patient care, and by volunteering for WLIs they help keep waiting times down. However, for a few, WLI payments can serve as a disincentive to working more efficiently because they face a loss of earnings."
His claims are supported by the experience of some NHS trusts.
Managers at Mid Staffordshire NHS Trust tried to reduce the rate for overtime for orthopaedic surgeons from £1,000 to £500 for a four-hour session. But minutes from official meetings showed consultants would be "downing tools" if they did so. In the end, managers had to compromise on a fee of £750.
Paul Flynn, from the British Medical Association, admitted some of the higher sums "sounded unhealthy", but pointed out research by the union also suggested consultants were doing six hours a week extra for free.
He also rejected suggestions that consultants were blocking moves to make hospitals more productive.
"WLI is a quick fix and consultants certainly would not want to come to rely on the payments as they are unpredictable."
He said hospitals could reduce the reliance on overtime by easing the load on consultants by recruiting extra staff or giving admin tasks and duties such as routine follow-ups to other staff.
But Professor Alan Maynard, an expert in health policy from York University and former chairman of a hospital, said NHS trusts often faced a "challenge" managing consultants.
"They don't always keep to their job plans and then get to do the overtime. I think there needs to be much more transparency about consultants' pay.
"The public are just not aware of the sums they can earn. If the data was published it would put pressure on them and reduce some of the figures we are seeing."
News of the overtime payments comes after the BBC reported at the end of last year that doctors were getting bonuses of up to £75,000 a year.
It means overall pay, once basic salary, bonus and overtime are totted up, can be well in excess of £200,000 a year.
The Department of Health said it did not want to comment on individual payments.
But a spokeswoman said: "We expect the NHS to increase productivity and improve health outcomes - this includes making effective use of consultants' time.
"Consultants and managers should work together to ensure that clinicians' time is planned cost effectively whilst delivering high quality patient care."