Growing pressure on health services has led to a "state of unease" in the medical profession, a leading regulator has warned.
A new report by the General Medical Council (GMC) also found there was a "dangerous level of alienation" felt by doctors in training which had increased because of industrial action.
It highlights the "intense pressure" of £2 billion in hospital deficits alongside falling performance figures for access to A&E, planned operations and ambulance response times as having a corrosive effect on morale.
Despite some bleak findings it stressed UK healthcare "remains among the best in the world" and the vast majority of doctors were not complained about to the GMC.
Additionally, figures show women are edging closer to comprising half of all registered doctors and medicine is becoming more ethnically diverse as a profession.
An NHS Employers spokesman welcomed the "insight the report gives into the huge financial and service pressures the NHS is under".
The sixth annual report, The State Of Medical Education And Practice In The UK, was released on Thursday.
The introduction reads: "There is a state of unease within the medical profession across the UK that risks affecting patients as well as doctors.
"The reasons for this are complex and multi-factorial, and some are long standing. Yet the signals of distress are unmistakeable."
The NHS Employers spokesman added: "We know insufficient social care funding is an immediate threat to the NHS and the wider health and care system putting increasing pressure on frontline staff and patients.
"We need the Government to incentivise greater coordination between local authorities and the NHS and to invest more in out-of-hospital health and care.
"This report also highlights our reliance on foreign-born workers who are a hugely valued and appreciated part of the workforce caring for service users and patients."
The GMC sets regulations and standards, oversees medical education and training, and intervenes when doctors may be putting patient safety at risk.
The report adds: "There appears to be a general acceptance that the system cannot simply go on as before - there does need to be early and concerted action.
"Everyone wants a health service that is efficient, effective and compassionate."
The regulator said it had begun a "special review" into making postgraduate training for doctors "more flexible" in the future.
A Department of Health spokesman said: "The dedication and sheer hard work of our NHS doctors is absolutely crucial to delivering world-class care for patients.
"As the report makes clear, the standard of care provided by doctors working in the UK remains among the best in the world - 1.6 million more NHS operations now take place each year compared to 2010 and hundreds of thousands more people are seen in A&E within four hours.
"The Government is investing £10 billion to fund the NHS's own plan to transform services for the future - central to which is listening to the concerns of staff."