Changes effected in immigration rules and lowering of working hours for trainees have resulted in a serious shortage of doctors in the UK.
The British Medical Association (BMA) has uncovered Department of Health data that estimates there was a 5 per cent shortfall at the end of 2008.
In some cases, hospital departments had to rely on just six junior medics to do the job of ten.
The new immigration system prevents people from outside the EU from coming to train as doctors in Britain.
The situation might have got worse this year as a result of a new European Working Time Directive, introduced in August, which prevents the UK's 60,000 trainee doctors from working more than 48 hours a week.
Dr Shree Datta, the new leader of the BMA's Junior Doctors Committee, said: "Inadequate staffing is putting a huge strain on the NHS. A football manager would not start a match with 10 men. Yet many junior doctors work in understaffed teams every day.
"The problem of understaffed rotas has worsened because the government has mishandled changes to the immigration system leading to many overseas doctors, who used to fill the staffing shortfall, leaving the UK. Poor preparations for the working time directive are likely to have exacerbated the problem."
The deaths of between 400 and 1,200 patients at Mid Staffordshire Hospital between 2005 and 2008 were blamed, in part, on a lack of staff.
A report by the watchdog the Health care Commission, published in March, found that patients had been left in their own excrement while reception staff were expected to judge the seriousness of cases in A&E.
Dr Datta said: "Inadequate staffing levels were a key factor in the appalling standard of care exposed at Mid Staffordshire Hospital. Doctors working on understaffed rotas have serious concerns about standards of patient care.
"For too long the NHS has relied on junior doctors working beyond their contracted hours, the time has come to stop papering over the cracks and deal with the issue.
"We cannot continue to rely on junior doctors working extra unpaid hours to prop up our health care system.
"Hospitals unable to cope with the challenges of the working time directive need to take a close look at how they organise staff rotas."
A Health department spokesman dubbed the BMA's data as outdated and claimed that recruitment this year was higher than ever before with hard to fill specialties such as obstetrics and paediatrics achieving 99 and 98 per cent fill rates.
He also said that international recruitment was still possible where there were no EU candidates for the post.