The cost of paying temporary doctors to work at accident and emergency units in England increased by 60% in three years as hospitals struggle to find permanent staff.
Data obtained by the Labour Party showed that spending on locums was £83.3 million last year, a rise from £52 million in 2009-10, the BBC said.
Agency doctors are employed for almost one in 10 consultant shifts and up to one in six more junior posts, the figures reveal.
A locum can earn £1,500 a shift, more than four times what it would cost to employ a permanent doctor in the same role.
Doctors groups said the situation was "absurd" and damaged morale.
Dr Cliff Mann, president of the College of Emergency Medicine, said such spending was "unwise".
"It is not an efficient way of spending NHS money and can be damaging for morale when doctors work alongside other, sometimes less qualified doctors, who are earning much more," he told the BBC.
"But this has really been building for the past decade. There has been a lack of job planning and it is now very hard to attract doctors to this speciality."
According to the college in the last three years A&E units have filled just half of decision-making posts, with 383 specialist registrar posts vacant, The Times said.
Dr Mann told the newspaper: "We've only recruited 50% for each of the past three years. When people say there's no money, there is - we're throwing money down the drain. It's absurd. The only people who benefit from this are the locum agencies."
He said that A&E units were trapped as doctors realised they could earn almost four times their normal shift rate by working as a locum at a different hospital.
The figures were uncovered after Labour received data from 108 of the 145 hospital trusts it questioned under the Freedom of Information Act.
Shadow health secretary Andy Burnham said the increasing costs were linked to the Coalition's "disastrous" reorganisation of the NHS.
He told the BBC: "This government is guilty of gross mismanagement of the NHS. They are paying more for an A&E service which is getting worse by the week."
The College of Emergency Medicine believes unsocial hours and increased pressures on A&E departments have made it a less attractive prospect for doctors, the BBC said.
Last week it was revealed that around two thirds of the 144 trusts that run major A&E departments are missing targets of seeing patients within four hours of their arrival.
Mr Burnham denied that the current problems were a hangover from the Labour government because it takes six years to train medics to work in A&E.
He told the BBC Radio 4 Today programme: "The problem has got significantly worse since 2010.
"Doctors were in training when the Government came in to power. It should have been working then to attract those doctors into A&E.
"It could have done more to give them reasons to go into A&E and now what they have done is, because of the poor planning, the loss of planning in the system, because of the reorganisation, the NHS is now trapped in a vicious circle."
Health Minister Dan Poulter told the programme: "There has been for many years a problem. It was first flagged up in 2004 under the previous government, about recruiting doctors into A&E. It takes six years to train A&E doctors so this well pre-dates the current Government.
"The good news is there are now more permanent doctors than there were before 2010. We have seen a 20% increase in the number of consultants and there are 352 more doctors working in A&E."