The General Medical Council’s annual report said that many regions and specialities relied on foreign-trained doctors, who could leave the UK. It added that there were too few doctors to treat rising numbers of patients, and doctors were being “pushed beyond their limits”.

The State of Medical Education and Practice showed that 54 per cent of junior doctors took a break after finishing foundation training, a rise from 30 per cent in 2012. “Goodwill and commitment to always go the extra mile” kept the NHS running, it said. “This level of sacrifice is neither right nor sustainable.”

The number of doctors on the medical register has grown by 2 per cent since 2012. Over the same period in England there has been a 27 per cent increase in patients going to A&E, and the GMC said that an ageing population was putting pressure on services.

While the number of UK graduates on the medical register rose by more than 10,700 between 2012 and this year, the rise was offset by a fall of 6,000 in foreign-trained doctors.

Charlie Massey, chief executive of the GMC, said: “We have reached a crucial moment — a crunch point — in the development of the workforce. The decisions that we make over the next five years will determine whether it can meet these demands.”

A fifth of doctors in training said they felt short of sleep while working. In 2014, when 43 per cent of new doctors took a break from training, 22 per cent took a one-year break and 8 per cent took a two-year break. Others may never return. More than half of those taking a break said that it was because of burnout, and most wanted a better work-life balance.

The GMC said that reducing the pressure on doctors and improving the culture and making jobs and training more flexible would be vital to recruiting and retaining doctors.

In the east of England 43 per cent of doctors were trained overseas. In the West Midlands the figure is 41 per cent, and 38 per cent in the East Midlands. More than half, 55 per cent, of specialists in obstetrics and gynaecology trained overseas.

About 14 per cent of doctors in the UK trained in south Asia, but their numbers have dropped by 7 per cent since 2012. The number of doctors from Africa, Australia, New Zealand and North America also fell.

The Department of Health said: “The NHS has a record number of doctors — 14,900 more since May 2010 — and we are committed to supporting them by expanding the number of training places by 25 per cent.” The department was working to improve retention, it added.

BEYOND THE STORY

The health service turned to Britain’s former colonies in South Asia during labour shortages in the 1960s and again in the 2000s when there were too few homegrown recruits.

Today, too, it leans heavily on overseas doctors. A third of doctors in the NHS trained outside the United Kingdom. The reliance has raised concerns that the NHS may be fuelling a “brain drain” in poorer countries where doctors are desperately needed, although others argue that training in the UK can improve those doctors’ skills.

It comes down to the simple fact that the UK does not train enough doctors to meet the demands of its population.