Juniors say they are hard-pressed
Junior doctors are being asked to work longer hours, often unpaid, because of staff shortfalls, the British Medical Association has warned.
Its survey suggests three in ten work on teams with at least one vacancy. It warns care could suffer and of possible bullying and harassment of doctors.
The BMA blames problems with a recruitment system introduced in 2007.
The Department of Health acknowledged the problem, saying it was working with NHS Trusts and doctors to solve it.
The BMA has issued guidance to junior doctors asking them to be alert to any changes in their working rotas.
It believes that, in some cases, there is potential for an increase in bullying and harassment as juniors are asked to cover for unfilled posts.
Some doctors who replied to the surveys said that there were as many as five unfilled vacancies in their specialties, increasing their own workload substantially.
Ram Moorthy, chairman of the BMA's Junior Doctors Committee, said: "It's fundamentally wrong for junior doctors to be pressured into working excessive hours.
"This was a problem that employers and the government could and should have foreseen, and it's unfair that doctors are having to prop up rotas without being paid for it. If the problem continues it can only damage the quality of patient care."
The problem has arisen, the BMA believes, because Trusts were given a single opportunity to recruit new juniors last year, and have not been able to fill posts which have become vacant in subsequent months.
Hospital consultants say they also expect to have to cover extra work as a result.
Dr Jonathan Fielden, chairman of the BMA's Consultants Committee, said: "Consultants in many trusts are working under extreme pressure to hold the service together for patients.
"Whilst we condemn bullying in any circumstance, consultants and employers must work together constructively to solve this problem and support our junior colleagues at this stressful time."
The Department of Health said it had conducted its own survey of strategic health authorities in February in an effort to gauge the extent of the problem.
A spokesman said: "It is worth bearing in mind that the NHS employs around 120,000 doctors in England and, whilst some Trusts have reported issues, many haven't.
"There have always been some problems staffing some rotas in shortage specialties.
"We understand the theory that the single timetable for specialty training recruitment in 2007 might be a contributor and that is partly why we are moving to a three-phase timetable in 2008, but there may be other factors.
"We are talking to the NHS, to the medical profession and others about potential solutions."
Shadow health secretary Andrew Lansley MP said that it was "unacceptable" that junior doctors were overstretched.
"The measures deployed by the government to try and mitigate the impact of their doctor training shambles are creating more problems."