GPs are becoming "absolutely weary" and burnt out as a result of increasingly "intolerable" workloads, MSPs have been told.
The early signs of a workforce crisis are becoming apparent in the profession, the deputy chair of the British Medical Association's Scottish GP committee warned Holyrood's Health Committee.
Dr Andrew Buist was attending the committee to give evidence on health inequalities and access to services.
He said general practice was losing older staff and failing to attract as many young doctors, while those who left to have families were not returning.
GPs are also turning to part-time hours to cope with the job, Dr Buist said.
He told the committee: "We are seeing the early signs of a workforce crisis.
"General practice has lost popularity with the young doctors coming into the profession. Older doctors are leaving slightly earlier, in their late 50s rather than hanging on into their early 60s, and we are also losing doctors in the middle of their careers."
Female GPs outnumbered males across UK for first time, he said.
Dr Buist continued: "Women, when they go away to have families, they are not coming back into the profession, and one of the reasons for that is they are frankly burnt out.
"The workload is becoming intolerable. It is not something that is just particular to practices providing care in more deprived areas, it's across virtually the whole spectrum of general practice."
He added: "I have been a general practitioner for 20 years. Yesterday I saw 40 patients face-to-face, it was an 11-hour day, there was almost no time, lunch was five minutes.
"That is a marked contrast with 11 years ago. In those days I would have had two hours to myself in the middle of the day.
"General practitioners are absolutely weary. They are increasingly working part-time to try and cope with the demands, and we need to do something quite quickly to stabilise the workforce."
Dr Buist warned that Scotland could start to see a situation being experienced in other parts of the UK, where locums were being used, at double the cost, to provide a practice.
"You are going to start seeing that in other areas, it is going to particularly hit rural areas first, then deprived areas and the out of hours services," he said.
"It will also make locums increasingly difficult to find, and that is important because it is locums who will backfill to allow the GPs away from their practice to get involved in health and social care integration."