Of 507 GPs who responded to a GPonline poll, 23% said they were aware of at least one specific case in which a patient at their practice had come to harm because NHS services were overstretched this winter.
Of more than 100 GPs who explained how patients registered at their practice had come to harm, almost a third cited patients being released too early from hospital as a factor. A similar proportion highlighted delays with ambulance services.
Six respondents said patients had died soon after delays in care or inappropriate early discharge.
Testimonies from GPs about patients who came to harm this winter are harrowing. Several reported patients with sepsis - including toddlers - facing long waits for an ambulance, in some cases more than an hour and a half.
One GP reported a '90-minute wait for an ambulance for a patient with sepsis who then died within 24 hours of admission'.
Another said waits for ambulances had risen to '90+ minutes' and that two patients with 'all the red flags for sepsis' - a toddler and a woman who had recently given birth - had faced delays in care. The GP added that this had meant 'care of all other patients on those afternoons was significantly delayed due to needing to focus resources (GP and nursing staff) on the sick patient'.
A third GP wrote that 'long ambulance delays' had meant that two patients with sepsis 'had to wait well over an hour'. She added: 'One subsequently died. One patient waited well over an hour for an ambulance and had a STEMI.'
Another patient was reported to have died after an MI following discharge from hospital due to 'bed pressures', while another patient who died was reported to have been 'inappropriately discharged to home or a nursing home just before the new year bank holiday.
Among GP partners, 30% said they were aware of patients registered with their practice who had come to harm because of winter pressure. More than four in five of all respondents said they were concerned that patients had been put at risk by pressure on the health service in their area this winter.
GP leaders said the findings were 'further evidence of a system under massive pressure'.
Three quarters of GP partners responding to the poll said their practice had struggled to cope this winter as flu rates hit the highest level for seven years and the cancellation of elective care in hospitals through January drove up demand.
General practice is already under chronic strain, with the latest workforce data confirming another drop in GP numbers, and more than 1,100 GPs seeking help from a burnout service over the past year.
GPC chair Dr Richard Vautrey told GPonline: 'These findings provide further evidence of a system under massive pressure and despite the hard work and dedication of healthcare staff in the community and in hospitals, patients are ultimately suffering as a result.
'While the winter brings additional problems, these pressures are now impacting care throughout the year and there is a need for long-term, recurrent increased funding across the NHS so that all services can expand their workforce to be in a better place to meet the growing needs of an aging population.'
The findings come after five successive weeks in which official NHS data have shown that hospital bed occupancy rates were at around the 95% mark - well in excess of the 85% target considered safe.
An NHS England spokesman said: 'Winter preparations started earlier than ever before this year with local groups of hospitals, community services, primary care and other NHS organisations developing robust plans to manage expected increased pressures, as well as create contingency plans to cover exceptional surges in demand. And practices are being supported with an additional investment of £20m to help primary care manage winter pressures.'
A DHSC spokesman said: 'The government supported the NHS this winter with an additional £437m of funding, and gave it top priority in the recent budget with an extra £2.8bn allocated over the next two years.
'We know GPs are busy – that’s why we are committed to an extra 5,000 doctors in general practice by 2020 — supported by investment of an extra £2.4bn a year to improve care and deliver better patient access.'