Overseas doctors, mainly from the Indian sub-continent, demonstrated outside the Department of Health in London on Friday to protest against new rules forcing them to leave Britain.
Immigration regulations announced last month mean doctors from outside the European Union will no longer be able to train in Britain without a work permit, a change which could hit up to 20,000 doctors.
Around 70 percent of those affected come from the Indian subcontinent, a traditional recruiting ground for Britain's state funded National Health Service.
During the protest, attended by around 250 doctors, a petition was delivered to Prime Minister Tony Blair's nearby Downing Street residence, complaining about the "sudden withdrawal" of work permits. Some said they had borrowed large sums of money to come to Britain which would take them many years to pay off in India.
"I am five thousand pounds in debt. I am in financial crisis", said Dr Alok Kalyani, from north-west India.
Kalyani said he had been in the final round of interviews for a hospital training post when the new rules came into force, and was told he was no longer eligible for the job. Medical trainees work for up to seven years as junior doctors before qualifying as consultants or general practitioners.
Shortages of doctors in the past meant Britain encouraged overseas medics to train in the NHS, but a rise in the number of home-trained medical students has increased competition for suitable training jobs.
"The new rule is unfair and unjust, and leads to discrimination against doctors who have been the backbone of the NHS since its inception," said Dr Ramesh Mehta, president of the British Association of Physicians of Indian Origin.
Mehta said 15,000 of those affected by the change were in the middle of their training.
"Many of them have children in school, many have bought houses. Suddenly, everything is gone."
Hospitals hiring trainee doctors now have to give priority to applicants from the UK and other European Union countries.
Junior doctors from other countries will only get work permits if it can be shown they have specialist skills unavailable elsewhere.
"We've been told for some time that we should be more self sufficient in doctors and not suck in doctors from overseas," Health Minister Lord Warner told the BBC.
"There's been a 70 percent increase in the number of medical school intakes over the last seven or eight years.
"We have to ensure there are postgraduate specialist training posts for our own UK graduates."
The British Medical Association, which represents doctors, said the work permit change had been introduced without adequate consultation.
"These are doctors who have devoted a huge amount of talent, time and energy to the NHS, and are now facing the prospect of enforced departure without any gratitude from the UK," said Dr Edwin Borman, chairman of the BMA's International Committee.