GP leaders said the findings were another sign of the huge pressure facing general practice every day, warning that patient safety and doctors' wellbeing were being compromised to keep up with demand.
Nearly two thirds of GPs (62%) take no breaks during an average clinical session, the survey found. Just under a third (32%) of the 644 GPs who responded took one break, while 5% took two, and a handful reported more.
Many GPs responding to the survey said they were often unable to take breaks at any point during a full working day. Scheduled breaks were often swallowed up when sessions ran over time and many respondents said they chose not to take breaks because to do so would mean their working day would not finish until late at night.
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Just a quarter of GPs reported that their practice took steps to ensure they take breaks, while 65% said their practice did not - and a further 8% were unsure.
The results reflect growing pressure on general practice after a 4% drop in the full-time equivalent GP workforce over the past two years, while the patient population has aged, and grown by almost 1.5m.
Meanwhile, more than half of GP consultations with patients aged over 18 now involve multiple morbidity - making them almost impossible to tackle within a standard 10-minute visit.
GPC chair Dr Richard Vautrey said: 'This is a sign of the daily pressure GPs are under as they try to fit more and more into each working day, a day which itself can grow longer and longer as the workload that needs to be completed expands.
'It's not good for doctors' health and wellbeing to work in this way and can ultimately lead to an increase in burnout as a result. More needs to be done to give GPs time to rest, reflect and recharge as by doing so it will enable better patient care.'
RCGP chair Professor Helen Stokes-Lampard said: 'If GPs were airline pilots responsible for the safety of hundreds of passengers we would be prohibited from carrying on doing our jobs if we were exhausted, yet this is increasingly the norm for hard-pressed GPs.
'General practice is a "safety critical industry", but we are being expected to work longer and longer hours seeing more patients to fulfil steadily rising demand, without a comparable increase in resource. Inevitably it is our breaks - and ultimately our own wellbeing - that is being sacrificed in order to keep pace with demand.
'As GPs, we are incredibly dedicated to our patients, but worn-out doctors are potentially dangerous and there is a limit beyond which we cannot guarantee that we are practising as safely as we want to be, which in turn builds up stress and anxiety.
'The college has long been calling for a warning system, similar to the ‘black alert’ in hospitals, to be implemented for GPs so we can signal when things are getting too much for us. This is becoming more of a priority by the day.
'But ultimately, we need more investment and far more GPs in the NHS so we can do our work safely and protect our own health wellbeing as well as that of our patients.'
GPonline reported exclusively earlier this year that the GP Health Service - set up to offer support to doctors struggling with mental health, stress, burnout, addiction and other problems - had supported more than 1,100 doctors in the 12 months after it opened its doors on 30 January 2017.
Board papers published by NHS England last week revealed that officials expect the first recruits from an international GP recruitment programme to begin work in September, with the health service still committed to the 2015 target of increasing the GP workforce by 5,000 by 2020/21.
The board papers highlighted plans for extra CCGs investment in primary care, infrastructure projects, investment in pharmacists working in primary care and work to help GPs and practice staff to 'maximise their time'.