GPs have been forced to reject patients for routine appointments as pressure on practices means they can only accept urgent consultations.
According to a new survey of 769 GPs, nearly 17% said they had to turn down patients attempting to see a GP for a routine matter.
Some GPs have no routine appointments available for the next four weeks and are using telephone triage to identify those who require consultation for an urgent matter.
Dr Jennifer Lyall, a GP in Cumbria, said her practice was one resorting to this due to a shortage of GPs.
She said: "At that time we had only two permanent GPs for a 7,000-patient practice."
The British Medical Association (BMA)'s GP Committee said the data - collected by Pulse, the publication for GPs - was "further evidence of the pressures practices are under".
Dr Martin Tant, a GP in Lincolnshire, said: "When we ran out of appointments for the four following weeks, we ceased offering appointments beyond four weeks in the future.
"We noticed a large rise in patients who did not attend their appointment, having booked this far in advance."
While 127 survey respondents said they had to reject patients attempting to see a GP for a routine matter in the last 12 months, 543 respondents said they had not had to do so while 99 did not know.
Health secretary Jeremy Hunt pledged in September 2015 there would be 5,000 extra GPs in England by 2020.
However the number of full-time equivalent GPs in the workforce has decreased by more than 1,000 since then.
The BMA has called for limits to be agreed for the number of consultations a GP can safely undertake in a day.
BMA GP Committee chairman Dr Richard Vautrey said: "This is further evidence of the pressures practices are under, with growing demands for appointments not being matched with an ability to provide them due to the continuing recruitment and retention crisis in general practice.
"Over recent years, the number of consultations has been steadily rising while the GP workforce has been declining.
"Surgeries are now left in the position where telephone triage is the only method by which staff are able to handle this demand in a safe manner - but this can result in increased stress for many GPs as they try to manage so many patients each day."
Professor Helen Stokes-Lampard, chairwoman of the Royal College of GPs, said: "GPs up and down the country are fighting fires, delivering care to patients with urgent health needs - but this often means patients whose problems aren't necessarily urgent are having to wait longer and longer.
"Our concern is that a problem might not be urgent initially, but becomes urgent further down the line if it isn't dealt with - GPs want to identify and treat problems early, so that it doesn't come to that.
"It's huge testament to the hard work and dedication of GPs and our teams that more than 70% report not having had to turn a patient with a routine issue away, but for others, there simply are not the consultations to offer, or the GPs to deliver them.
"We're trying our best, and utilising innovative schemes, such as Skype or telephone triage or same-day booking systems, to see as many patients as possible, prioritise their needs, and if appropriate, suggest an alternative healthcare professional in the community.
"But the pressures GPs and our teams are working under are unsustainable - our workload has escalated in volume and complexity in recent years, but investment in our profession is less than it was a decade ago, and GP numbers are actually falling."
An NHS England spokeswoman said: "With 33,600 GPs in England, this tiny survey represents less than 3% of those GPs, and, of those, fewer than a fifth said they have taken this action.
"We understand the pressures general practice is facing which is why the NHS is investing £2.4bn extra in GP services, growing the number of new doctors entering general practice, and rolling out evening and weekend appointments to patients across England over this coming year."
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