In September 2018, 29.7% of GPs in salaried or partnership roles were working full time or more than full time, according to figures published by NHS Digital.
The proportion of GPs working full-time or more has dropped sharply over the past three years, the figures show - falling from 34.3% in September 2015.
GP leaders said the figures reflected a workforce under extreme pressure, with GPs forced to reduce their working hours to manage risk and workload.
However, although the figures suggest that GPs are reducing their working hours, the data are based on the hours doctors are contracted to work - and do not show actual time worked.
A GPonline poll at the end of 2018 revealed that almost four in five GPs said they worked more than their contracted hours - with half of those reporting that they complete 30% or more hours than they are contracted to provide.
The official data show that among partners, the proportion working 37.5 hours or more dropped from 42% in September 2015 to 38.9% in September 2018.
Among salaried GPs, the proportion working full time or more dropped from 15.1% to 12.3% over the three-year period.
GPC chair Dr Richard Vautrey told GPonline: 'This will require more GPs to be trained, as well as dealing with the workload pressures and the pensions issues that are driving this change.'
He addressed the issue of GPs reducing the hours they were contracted to work in his speech at the England LMCs conference in November.
The GPC chair said at the time: 'It’s no wonder that so many GPs are reducing their clinical commitment in order to reduce their risk. But they are also doing this to help manage workload pressures, to help get their head back above water, to achieve a better balance in their professional lives and to be able to sleep better at night because the risk of mistakes and errors has been reduced.'
But he hit out in the speech at people calling GPs who work 'five or six intense, stressful, almost never-ending sessions a week' part time - declaring this was 'an insult'.
'These GPs who still work more hours than most people do in a week need our praise and thanks, not off-hand and unwarranted criticism. GPs are right to take steps to work in a safer and more sustainable way. It’s the way to enable more of our colleagues to stay in the profession rather than leaving altogether,' Dr Vautrey told the conference.
RCGP chair Professor Helen Stokes-Lampard said: 'We have a record number of junior doctors currently entering GP training, which is hugely encouraging.
'But current pressures in general practice often mean that working full time simply isn’t sustainable, and it would be unfair to suggest that those choosing to work part time are somehow contributing to workforce issues. It’s also important to remember that some people who work part time clinically have portfolio careers and are contributing to the NHS and patient care in other areas of healthcare.
'Less than full time in general practice often involves working more hours than the average full-time job, and our research has shown that 11-hour days in surgery are not uncommon – all of which is unsafe for our GPs, our staff and our patients.'
GPs who took part in the latest GPonline poll hit out at heavy workload. One said: 'It is increasing every year. No one works nine sessions any more as it is not possible to complete all the work associated with this - at least if you want to stay sane.'
Another wrote: 'I am lucky as I control my workload (locum/portfolio GP). I see my partner colleagues working way over their supposed sessional commitment, including many hours logging in from home. Number of consultations is one factor; complexity of those consultations is another.'
One GP 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 GP to work out-of-hours because of this.'