Patients are being put at risk by “stark” levels of exhaustion among junior doctors, laid bare in the first major survey since a new contract to make the NHS safer at weekends came into force last year.

The General Medical Council (GMC) warned nearly a third of junior doctors say they are exhausted before the work day even begins, according to the results of its annual nationwide survey of medical training.

Safety groups said the findings would be “concerning for patients across the country” as tired doctors are more likely to make mistakes.

They called on those in charge of medical education to act quickly to ensure doctors had time to care for themselves and their patients.

Protection for junior doctors’ training and welfare was meant to be central to the contract pushed through by health secretary Jeremy Hunt in the face of unprecedented strike action in 2016.

It has affected all junior doctors since October last year, and saw “guardians of safe working hours” introduced to offset concerns about the extra weekend and evening working it required.

But the GMC findings on burnout revealed a widespread culture of long and intense hours and heavy workloads, which are “affecting doctors’ training experience and their personal wellbeing”.

The regulator polled almost 52,000 doctors in training and 19,000 of their trainers across the UK.

In pictures: Junior doctors first all-out strike Show all 10 1 /10 In pictures: Junior doctors first all-out strike In pictures: Junior doctors first all-out strike Doctor in acute medicine, Melissa Haskins, holds up a 'I ain't afraid of no Hunt' sign whilst striking with other junior doctors outside her hospital, St Thomas' Hospital in London Getty Images In pictures: Junior doctors first all-out strike Accident and emergency junior doctor, Jennifer Hulse, holds a homemade placard outside St Thomas' Hospital as she strikes with colleagues in London Getty Images In pictures: Junior doctors first all-out strike Demonstrators and Junior doctors hold placards as they protest outside the Basingstoke and North Hampshire Hospital, in Basingstoke during a strike by junior doctors Getty Images In pictures: Junior doctors first all-out strike Demonstrators and Junior doctors hold placards as they protest outside the Basingstoke and North Hampshire Hospital, in Basingstoke during a strike by junior doctors Getty Images In pictures: Junior doctors first all-out strike A supporter displays a slogan on her bag during a junior doctors' strike outside St Thomas' Hospital in London Reuters In pictures: Junior doctors first all-out strike The picket line outside King's College Hospital in London PA In pictures: Junior doctors first all-out strike The picket line outside King's College Hospital in London, as thousands of junior doctors begun the first all-out strike in the history of the NHS after the Health Secretary said the Government would not be "blackmailed" into dropping its manifesto pledge for a seven-day health service PA In pictures: Junior doctors first all-out strike Junior doctors and supporters take part in a strike outside the Royal United Hospital in Bath Getty Images In pictures: Junior doctors first all-out strike Doctor in acute medicine, Melissa Haskins, holds up a 'I ain't afraid of no Hunt' sign whilst striking with other junior doctors outside her hospital, St Thomas' Hospital in London Getty Images In pictures: Junior doctors first all-out strike Dave Prentis, UNISON general secretary visits a British Medical Association picket line at Royal Sussex County Hospital in Brighton, to show support for striking junior doctors on the second day of the union's annual health conference PA

It found that almost a quarter of trainees (24 per cent) and one in five trainers said they feel burned out because of their work. Many said they were missing training opportunities to cover staffing gaps elsewhere.

Roughly one-third of trainees (32 per cent) said they were often or always exhausted in the morning at the thought of another day at work. Half said they were always worn out by the end of the day.

It also found one in five said that they feel short of sleep at work.

“Patients across the country will be concerned by these findings,” said Rachel Power, chief executive of the Patients Association. “Tired doctors make more mistakes – and patient safety suffers as a result. A vulnerable person in hospital wants to be cared for by well-rested doctors who are alert and capable of making the best clinical decisions for their patients.”

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Charlie Massey, chief executive of the GMC, said: “Training must be protected and it must be safe, and employers need to address this urgently. But it is also important that the wider issues reported in our surveys, around work-life balance, burn-out and exhaustion, are acted on.

“We can put off no longer the need to give doctors in training – who make up a fifth of all doctors – the resources they need and deserve.”

The GMC said it is working to ensure doctors were confident that if they raised staffing concerns these would be addressed, but said “it will take investment” to solve these issues.

Theresa May recently announced a £20bn increase in NHS funding over the next five years, but a report by the group NHS Providers warned that nearly all of this would be used up repairing the damage of eight years of austerity.