Senior GP Helen Stokes-Lampard voices fears for services
Britain's leading GP says she is "profoundly concerned" about how doctors will cope with demand over the busy winter period.
Helen Stokes-Lampard, chair of the Royal College of GPs Council, said general practice was "skating on thin ice", warning: "Something has to give".
Some people wait weeks to see a doctor, with potentially serious results, the Staffordshire-based GP said.
NHS England said GPs would be getting extra funding to extend services.
'The big fear'
Dr Stokes-Lampard told the Press Association some patients were already waiting two or three weeks to see GPs for non-urgent matters such as suspect lumps or bleeding problems.
But if they wait three to four weeks "the non-urgent stuff may be becoming urgent," she added.
"With lumps or bleeding problems or things that could be signs of serious disease, my profound concern is that people will delay seeking help for things that could potentially be life-threatening or life-changing if they are not tackled swiftly.
She went on: "As a service that is already skating on thin ice - a service that is stretched incredibly thinly - something has to give.
"Well, what do you do? If you've got to deal with people who are acutely sick on the day because people need help, then chronic disease management will disappear."
Describing chronic disease management as "the most phenomenal success story of the NHS", she added that her "big fear" was that this would be affected "because we are too busy fire-fighting the urgent stuff".
It that happened, "The knock-on consequences could take years to manifest but they will be very serious indeed," said Dr Stokes-Lampard.
Speaking to the Today programme on BBC Radio 4, she said GPs want to do the best for the patients so it causes "enormous stress as well as fatigue in us when we are fire-fighting all the time".
She said the situation was getting worse because the service is "stretched even more thinly than ever" due to a lack of funding over the last 10 years.
Dr Stokes-Lampard recognised that NHS England had promised to invest more money into GP services - but it had yet to reach the front line.
She said similar pledges had yet to be made in Wales and Northern Ireland, while some investment had been promised in Scotland.
She went on: "We need the promises in those countries that haven't had them and where we have had the promises we need them fulfilled.
"We need every penny, every person promised getting out there and that will shore up the service because if general practice goes under then the hospitals fall down very quickly too because they will be completely inundated with patients and that's a risk to the whole NHS."
Dr Richard Vautrey, deputy chairman of the British Medical Association's General Practitioners Committee, said the issues faced by GP surgeries were a year-round problem.
He added: "It's particularly acute at this time of the year because of the increase in respiratory illnesses and falls and trips and other types of illnesses that are impacted by the cold weather.
"But it is a pressure that is on every surgery almost every day of the week, throughout the year and it's something we have to tackle and we have to tackle urgently."
Labour described the situation as "extremely worrying".
Shadow health minister Julie Cooper said GP surgeries were "overwhelmed by ever-increasing demand".
"Add to this a chronic shortage of GPs and a crisis in recruitment and the result is a service that is at breaking point," she said.
An NHS England spokesman said: "Of course over the Christmas and New Year period the top priority has to be medical emergencies, but the RCGP are right to remind everyone of what they describe as the 'most phenomenal success story of the NHS'.
"That's why GP services are on track to receive an extra £2.4 billion in real terms investment by 2020 to build on this track record of success and expand access to convenient appointments throughout the week."