The pressures of working in overcrowded A&E units have led hundreds of doctors to quit the NHS for Australia, according to a Guardian newspaper report.
The number of young doctors trained in the UK or Ireland but now working in Australian A&E departments has soared by 69% from 285 in 2008 to 481 in 2012, a recent study shows.
Dr Cliff Mann, president of the College of Emergency Medicine, which represents A&E doctors, said the growing exodus of registrars represented "a colossal loss of talent by A&E units which cannot afford to lose them" at a time when demand from patients has reached unprecedented levels.
He said the trend was "an unacceptable waste of taxpayers' money, because each of these UK-trained registrars has cost about £610,000 over the five years of their medical degree and subsequent five years as a junior NHS doctor".
There are now so many registrars from the UK and Ireland in Australian emergency departments that they comprise almost one in four (23.1%) of the workforce there, according to the Australian College of Emergency Medicine.
Traditionally many young British doctors have spent a year or two down under, before returning to work in the NHS. But a second, separate study of all 364 A&E registrars in the state of Victoria has found that 68% of them are from outside Australia, and 72% of those intend to stay there permanently.
If that figure is borne out, that would represent a potential permanent loss to the UK and Ireland of 350 A&E doctors.
Dr Michael Sheridan, the lead author of the Victoria study, who is himself a Glasgow-born A&E consultant now working at a hospital near Melbourne, said the dramatic shift posed problems for the NHS.
Australia's high levels of A&E staffing make it a magnet for young doctors who want a less stressful working life than in UK hospitals, where gaps in the rota are a widespread problem, he said.
The NHS is hugely reliant on staff from outside the UK. Some 94,833 of the 259,719 doctors of all specialisms registered with the General Medical Council to practise here, 36.5% of the total, are from overseas, including 1,969 from Australia.
But, Mann argued, chronic understaffing in A&E units across the UK meant the NHS could not afford to keep seeing registrars heading to Australia.
"These figures tell us that it's not the medical speciality of emergency medicine that's the problem; it's the working environment in it in the UK that is. The working environment in A&Es is intense, unremitting and increasingly unrewarding, and unsustainable for the doctors who staff it," he said.
A&E registrars are voting with their passports and being welcomed with open arms in Australia. I'm not surprised more and more doctors are going abroad. And the more who do it, the more normal it becomes, so the more likely it is that more people will follow."
The 481 who have left are equivalent to almost two years' intake of A&E registrars by the NHS, Mann said.
There should be 260 new registrars each year. However, only half that number have been recruited in each of the past three years, as emergency medicine has become less and less attractive to young doctors, who are put off by the relentless number of patients and regular overnight and weekend shifts.
"NHS A&Es cannot afford to lose these hundreds of very capable doctors, especially as they are already spending about £100m a year on locum doctors, so we are paying twice and getting a worse service, as relying on locums means the quality of the system isn't as good as if you have a permanent workforce," said Mann.
He suggested that the NHS should consider offering A&E doctors incentives and rewards to recognise the particular strains of their work and make the specialism more appealing, such as long-service leave, sabbaticals, extra annual holidays and an earlier retirement age.
Dr Keith McNeil, chief executive of Cambridge University Hospitals NHS foundation trust, urged ministers to relieve the pressure on A&E units by relaxing the requirement on the NHS to treat 95% of patients within four hours of their arrival.
While some doctors and nurses go travelling after completing their degree, that is "generally because of a lifestyle choice and not because of poor conditions within the NHS", McNeil stressed.
Andy Burnham, the shadow health secretary, said the NHS's ability to plan to ensure it had enough of the right staff had been damaged by the coalition's controversial shakeup of the service.
"This was a monumental misjudgment," he said. "David Cameron dissolved organisations responsible for workforce planning and the result is an A&E recruitment crisis that has got worse and worse and worse on his watch."
Dr Dan Poulter, the health minister, who is also a hospital doctor, said both consultant and junior doctors' contracts were currently being revised "so that we better incentivise doctors to choose A&E as a career". He also cited Health Education England's recent decision to recruit 100 extra A&E doctors a year for three years, starting in 2014.
He said: "There are over 7,200 more doctors working in the NHS now than there were in 2010, including over 200 more consultants in A&E. Medicine has always been a mobile profession and some doctors will want to spend time travelling and gaining experience working overseas.
"So in context of more graduate doctors, there will be more who travel and work overseas for a period of time, but evidence to date suggests that the majority will return to work for our NHS, and bring back with them experience that will benefit British patients."