GP surgeries are operating in "a state of emergency" because of problems with resources and staffing levels, a leading family doctor said.
Dr Chaand Nagpaul, head of the British Medical Association's general practice committee, warned patients are "are being short-changed on a daily basis" in a speech at a conference in London.
Dr Nagpaul, who practises in the capital, told the special conference of Local Medical Committees that research found 90% of GPs felt their workload was damaging the quality of care they provided, something he said was "a disgrace".
GPs, he claimed, were having to deal with complicated cases in 10 minutes, treat a "conveyor belt" of up to 70 patients a day plus administration, with understaffed practices forced to continue to register patients.
"To put it simply, it is not safe to carry on the way we are, and which is why this conference is highlighting that general practice is quite literally in a state of emergency," he said.
"I'm constantly told by ministers that the greatest battle is getting money out of the Treasury. My message to the Chancellor is to use his financial nouse.
"Stop penny-pinching and be pound wise, grab yourself a bargain while there are GPs out there because once they're gone they're gone, since it costs £136 for all-in unlimited care and home visits per patient per year which is less than the price of walking through a single outpatient clinic door once."
GPs have clashed with Health Secretary Jeremy Hunt over his plans for a seven-day NHS. And last year Mr Hunt was forced to defend England's chief inspector of general practice after doctors called on him to resign.
Professor Steve Field, who is based at the Care Quality Commission (CQC), came under fire over comments he made saying he was "ashamed" of colleagues who provided poor care.
In a video message to the conference, Health Minister Alistair Burt said the Government was increasing funding for GP services by between 4% and 5% over the course of this Parliament and looking at measures to streamline bureaucracy, CQC inspections and the payment system.
He said: "I know that general practice is under pressure at the moment, I meet a lot of GPs up and down the country. But I'm also aware of what it is we are trying to do to help."