A total of 8% of so-called part-time GPs work between 37.5 and 45 hours per week, the poll revealed, with a further 2% reporting that they work between 45 and 50 hours.
Among GP partners, more than one in five (21%) of those working in part-time roles reported working longer than 37.5 hours per week.
For full-time GPs, 21% reported working in excess of 50 hours per week on average. A further 27% worked 45-50 hours per week, and a third of full-time respondents reported working between 37.5 and 45 hours per week.
> Most GPs worked beyond safe limit in 2018
A total of 210 full-time GPs and 308 part-time GPs responded to the GPonline poll.
The findings come just a day after GPonline revealed that most GPs delivered more than the maximum number of consultations per day considered safe by the BMA during 2018.
Responses from GPs who took part in the poll reveal the growing pressure the profession is under as the workforce continues to decline. This website reported last month that in the year to September 2018 the full-time equivalent GP workforce dropped by more than 200.
General practice is delivering more than 1m consultations per day, official data has shown, many of which are increasingly complex - with more than half of consultations with patients aged over 18 now involving multimorbidity - and therefore impossible to manage within 10 minutes.
Long working hours
One GP responding to the poll said: 'An eight-hour day is actuallly an 11- to 12-hour day and back to back with no breaks. Completely unsustainable - I have just left daytime general practice to work out-of-hours because of this.'
Another said: 'It is currently unsustainable and relentless. A reasonable percentage of what I have to do is driven by unfettered demand over which we have little control, as doing so would leave us liable to neglecting the all encompassing duties laid out in our contract.'
One GP wrote: 'The GP workload has increased over my whole working life. More paperwork, lengthened days and weeks, expectations of ever increasing number of consultations per day and more complex patients due to an ageing population, unnecessary targets, and fuelled patient demand.
'No increased funding, funding given for good initiatives but then taken away as soon as one starts to see the benefit from those initiatives. Expectations of instant benefit which is totally unrealistic, as most good initiatives take a few years of hard graft before benefits appear.'
GPonline reported last year that more than 1,300 GPs were receiving support from the GP Health Service, set up to support NHS GPs struggling with burnout, stress, addiction or other mental health problems.
One respondent to the survey said: 'It is unsustainable and despite loving being a GP until the past five years and having a minimum of 20 years before retirement age I have been actively looking for alternative work as I worry about my mental health if I have to continue like this.'
GPC chair Dr Richard Vautrey said this week: 'It's clear from these results that GPs continue to work excessively long hours, which all too often leaves them stressed and exhausted. In such situations the risk is that mistakes will be made, and no patient wants to be looked after by a tired doctor.
'This continued workload pressure is having an impact on recruitment and retention of GPs, and is one of the main reasons we continue to see a fall in GP numbers.'