The Government must invest in general practice to "lift the profession off its knees", one of the UK's most senior doctors has warned.
Dr Chaand Nagpaul said the "parlous plight of general practice today" means that action needs to be taken now, "not promises of targets in 2020".
Delivering a speech at the British Medical Association's (BMA) annual representatives meeting in Liverpool, Dr Nagpaul, who is chair of the BMA's GP committee, said a "renaissance" in general practice was needed if the profession ever hoped to attract new recruits to help the understaffed workforce.
He described the Government's pledge to make surgeries open routinely seven day a week as "unrealistic and illogical" as well as an "insult" to the thousands of GPs who already work seven days a week, 365 days of the year.
"This will damage quality by spreading an inadequate GP workforce so thinly, and replace continuity of care with impersonal shift work, and take GPs away from caring for older vulnerable patents," he added.
"And given nowhere in Europe offers state funded routine seven day 8(am)-8(pm) GP services, is it moral that we should use a deficit NHS budget profligately when we can't afford cancer treatments available in other nations."
In a swipe against Health Secretary Jeremy Hunt's announcement of a "new deal" for GPs last week, Dr Nagpaul said: "The only deal fit for general practice is one that will one that will lift the profession off its knees from the weight of unsustainable workload, not keel it over with more burdens.
"A deal with gives us increased core resources to do our jobs properly with enough time with patients to provide safe quality care, with more nurses, pharmacists, and healthcare staff to support us now not promises of targets in 2020.
"A deal that doesn't just give golden hellos to under-doctored areas when the truth is the entire UK is under-doctored when it comes to GPs."
Dr Nagpaul said a "starvation" in funding of general practice has come as GPs "have taken on the greatest growth in volume of care compared to any other sector in the NHS".
GPs are now seeing an estimated record 370 million patients a year, up 70 million compared to seven years ago, he said.
"The irrefutable fact is that demand has absolutely outstripped our capacity, and we simply don't have the GPs, appointments, staff or space to meet these escalating demands, set to increase further with a growing older population, and tranches of care moving out of hospital," he added.
"This has resulted in unsustainable workload, at a punishing pace and intensity. GPs work flat out 12 to 14 hour days without a break.
"We manage complex patients often with four different chronic problems, trying to condense an hour's worth in the impossibility of 10 minutes."
Dr Nagpaul told delegates the Government's pledge for 5,000 more GPs during this parliament "will be pointless if we lose 10,000 GPs in the same breath", referring to a recent survey by the BMA that found one in three of the 15,000 GPs questioned said they intended to retire in the next five years.
It was reported today that Mr Hunt told delegates at the Health+Care show in London that it was now recognised it would not be possible to train 5,000 GPs in such a short time and that the figure was the maximum aimed for.
A spokeswoman for the Department of Health said Mr Hunt was not going back on his pledge.
Among the motions passed by the BMA was one which recognises that the current 10-minute standard consultation time for GPs is "out of date, takes no account of changes in medical practice, is not fit for purpose and should be increased".
Doctors believe that the increasingly complex medical needs of patients mean they need more time for appointments.
The BMA's survey in April found that fewer than one in 10 GPs (8%) felt that 10 minutes is adequate.
Two-thirds (68%) said they thought it was preferable to provide longer consultations of greater quality, even if it means patients have to wait longer to see a GP.