A total of 66 out of 152 trusts declared alerts under the NHS operational pressures escalation framework in the week to 8 January, NHS England data show.
Six trusts declared a level four alert - the highest possible level, a step that indicates they are facing severe, rising pressure and that they are 'unable to deliver comprehensive care'.
Alerts declared by the other 60 trusts were at level three, meaning that the local health and social care system is 'experiencing major pressures compromising patient flow' and that pressure is continuing to increase.
GP leaders warned that the crisis facing hospitals was having a significant knock-on effect on GP practices that were already under severe pressure, and warned that an urgent rise in NHS and social care funding was vital to prevent the winter crisis spiralling into a year-round problem.
The figures come after health secretary Jeremy Hunt responded to claims from the British Red Cross that mounting pressure on the NHS amounted to a 'humanitarian crisis' by suggesting that seven-day GP services could help ease pressure.
The health secretary has also suggested that GPs could be drafted in to help ease pressure on hospitals, although how this could work remains unclear.
Trusts facing level four crisis alerts are spread across England, with two in the South of England region, four in the North of England region and two in the Midlands and East region.
GPC deputy chair Dr Richard Vautrey told GPonline that the hospital crisis varied from area to area, but he warned that hospital pressure was rebounding on general practice.
'There are widespread restrictions or freezes on referrals for routine operations or procedures,' he said. 'This creates delays for patients, and patients are coming back to practices because their operation has been put off, or because they haven't heard anything.'
GPs were under significant pressure not to contribute to hospital pressure by making basic referrals, he said.
Dr Vautrey added that with community nursing teams also struggling in some areas, practices also faced restrictions on referrals to those services. 'This has a knock-on effect on practices - where do you go for support?'
Practices were also facing high seasonal demand for services anyway, Dr Vautrey warned, on top of existing pressures from long-term underfunding and a workforce shortage.
He said: 'While there is intense scrutiny on hospitals and community nursing teams, there seems to be a real lack of support for GPs to maintain their services.'
The GPC deputy chair acknowledged that NHS England had recognised the problems were being driven significantly by a the lack of available social care support for patients, which had left many unable to be discharged from hospitals, creating a blockage that prevented further patients from being admitted.
He said: 'People will do their best to keep going. We have been warning about this for years - it was inevitable it would happen. The longer the squeeze on NHS and social care funding goes on, the more this will happen not just in winter but throughout the year.'
BMA chair Dr Mark Porter warned: 'It is extremely concerning that this many trusts in one week raised the alarm to say they can’t cope, and it shows the scale of the crisis in our NHS at the moment.
'Our hospitals are in the red, GPs are unable to keep up with the number of patients coming through the surgery door, patients are suffering and staff are working under impossible conditions. We urgently need the government to act now and put together a long-term plan to help solve the ever growing issues around staffing and funding the health and social care system as a whole.'
*Note: this story was updated to reflect a correction issued by NHS England to its data on hospital alerts. NHS England initially stated that eight trusts had declared level four alerts, but corrected this to six.
Photo: Donald Stewart