Thousands of trainee doctors in England and Wales cannot find posts, the British Medical Association has claimed.
The association has been saying since June that it was hearing from medics who could not find training posts.
Now a BMA survey of 635 doctors has found one in 10 had been unable to find a position, which the association says would translate to 3,000 across the UK.
But the Department of Health rejected the BMA’s claims.
It said evidence from the bodies which co-ordinate junior doctors’ training, postgraduate deaneries, showed just 103 medics who had completed their first postgraduate training year had not been able to find a post at the beginning of September.
But the BMA says that there is more competition for posts than usual this year.
It says this is because of an increase in numbers of doctors graduating from medical school and a rise in the number of overseas doctors hoping to train in the UK.
Some long-term posts may also be being phased out because of changes to medical training, it says.
The BMA said it had carried out the survey in a bid to get a clearer picture of how many doctors were affected.
It said around a third of doctors who had not found a post were no longer looking for work in the NHS.
The BMA said that, if this pattern applied across England and Wales, that would equate to a loss of around 900 doctors.
The association also said it had been contacted by over 300 junior doctors who did not take part in the survey who said they had been unable to find posts.
It says that the survey responses and anecdotal reports it has received show that at least 830 junior doctors could not find posts.
The BMA says there should be better workforce planning, and in particular is calling for a system where overseas doctors are not allowed to come to the UK until they have at least a provisional offer of a training post.
Dr Jo Hilborne, chair-elect of the BMA’s Junior Doctors Committee, said: “We know there’s a problem, and we’re keen to work with the government to help deal with it.
“These are people who are desperate to work for the NHS, and have spent years of their lives in training at a huge cost to the taxpayer.
“Patients’ healthcare needs are growing, the country is still short of doctors, and we should be doing everything we can to prevent their skills from being wasted.”
She warned that many doctors were currently on short-term contracts that expire in February, and further problems could occur then unless something was done.
A Department of Health spokesperson said: “The figures being quoted by the BMA are misleading.
“The Department of Health does not agree that “thousands” of UK trained junior doctors are unemployed, especially when job opportunities and training posts continue to be advertised each week.”
But Shadow Health Secretary Andrew Lansley said: “The government is in denial about this problem and have completely failed to address it.
“We urgently need to provide more resources to create senior training posts to redress the bottleneck.”