The Royal College of GPs (RCGP) said funding cuts over the past three years are already having a "disastrous effect on patient care" and that emergency measures need to be taken by the Government.
They said there has been a 7% drop in funding per person in England from 2010 to 2013, due to the £400 million fall in investment and population growth.
According to the figures, released ahead of the RCGP annual conference in Harrogate, investment in general practice fell to £8,459 million in 2012/3, from £8,865 million in 2009/10.
Dr Clare Gerada, chair of RCGP, who will address GPs at the gathering today, said: "Our figures should send out a warning to Government and the rest of the NHS that we will soon have a catastrophe on our hands if urgent action is not taken to reverse the decline in funding for general practice and provide GPs with an appropriate amount to spend on each patient every year.
"For years politicians, health professionals and patients alike have been saying that we must shift the centre of gravity of the health service away from hospitals, with more care delivered to patients closer to home, and a greater focus on prevention. But these figures show that we are in fact moving in the opposite direction.
"We are working our hardest to make sure that patients are not affected but the status quo is no longer an option. We must have an emergency package of additional investment for general practice to protect GP services and protect our patients from cuts to their care."
She also said that while more than 90% of patient contact within the NHS is with a GP, only 9% of the entire budget is currently awarded to general practices.
The analysis, from data produced by the Health and Social Care Information Centre, comes after Prime Minister David Cameron announced a £50 million trial to encourage longer GP surgery opening hours, with the aim of extending them from 8am to 8pm seven days a week.
Dr Gerada said: "General practice is the most cost-effective and efficient arm of the health service - GPs keep the rest of the NHS stable and secure. Once general practice starts to crumble, the entire NHS will follow with disastrous consequences for our patients.
"In August this year, the Government announced an additional £500 million over the next two years for A&E departments. What we need is our fair share of funding - at least 10% of the entire NHS budget and at least 10,000 more GPs - so that GPs can provide more services for patients in their communities."
A recent RCGP poll, carried out in August, found that more than 80% of GPs now say they have insufficient resources to provide high-quality care to their patients, with 47% saying they had already cut back on the range of services provided.
Dr Chaand Nagpaul, chair of the British Medical Association general practitioners committee, said:
"These figures, if accurate, confirm what most GPs experience on a daily basis - inadequate resources to meet ever rising patient demand, compounded by the pressures of an ageing population and care moving out of hospitals and into general practice.
"GPs are now working harder than ever before, carrying out 340 million consultations last year.
"The economic and bureaucratic straitjacket that many GPs find themselves in has led to a decline in morale and is unsustainable, with GPs unable to provide patients with the time, access and level of care that they deserve. The Government needs to rapidly invest in more GPs, staff and resources so practices have the capacity to meet rising demand."
Health Secretary Jeremy Hunt is also set to address the RCGP conference today.
A Department of Health spokesman said: "GPs do a vital job. Investment in general practice increased 1.3% last year but we know GPs are under pressure to do more with tight budgets.
"That's why this week we announced a £50 million fund for GPs who want to pioneer new ways of working, to help make the best use of their time.
"We have also asked Health Education England to work towards getting 50% of medical students to become GPs so they have more resources."
Dr Gerada told BBC Breakfast general practice was "at tipping point" with doctors overworked and exhausted.
"If we are working beyond 11 hours we are not safe," she said.
"You don't want a tired GP any more than a tired pilot or a tired surgeon. We can't keep expecting them to do more."
The medic said lack of GP funding has already manifested itself in bigger queues for patients, a longer wait for an appointment and delays getting through to the surgery on the telephone.
She added some services, such as counselling, are being cut because of the squeeze.