GPonline analysis of hospital data from NHS England shows that one in four hospital trusts declared a level three or four alert - high-level warnings signifying extreme pressure - for half the month of January or more.
A level three alert under the NHS operational pressures escalation levels (OPEL) framework means patient flow was compromised, while a level four alert means the hospital was unable to deliver comprehensive care.
Official data show that hundreds of urgent operations were cancelled in December, and pressures have continued throughout the first month of 2017 with under-pressure hospitals forced to delay non-emergency operations and outpatient appointments. In January the British Red Cross warned that NHS problems amounted to a 'humanitarian crisis'.
NHS winter crisis
Several hospital trusts declared high-level alerts every day in January, and more than half declared a level three or four alert on at least one day in the month.
GPC deputy chair Dr Richard Vautrey said the restrictions on hospital treatment had a big impact on general practice. 'Many patients who would otherwise be expecting to have surgery done or an outpatient appointment get cancelled, and they come back to the GP and ask why.
'This adds bureaucracy and extra appointments onto already overstretched GP services.'
Despite the focus on the winter crisis, Dr Vautrey warned that this now 'happens sadly throughout the year now'.
'The impact goes on much longer, especially on waiting times, especially for follow-up appointments with hospitals.' These waits in particular could be 'very significant in length', Dr Vautrey warned, because they were 'not part of the national monitoring scheme'.
Cancellations were less common for operations, he said. But people needing regular follow-up appointments faced long delays that left them coming back 'to their GP wondering what has happened and thinking they have been forgotten.
'It tends to be people for regular follow up - at the eye clinic, going to see a rheumatologist or cardiologist - the patient expects to be seen again in three or four months and often finds that the actual follwo up is in six or nine months.'
In terms of levels of illness, the winter crisis in 2016/17 had not been worse than usual, Dr Vautrey said. But he warned that pressure on beds from the reduction in nursing home places and cuts to social care had been the key factor that left hospitals unable to move patients out of beds.
He urged hospitals to give patients 'realistic timetables' to avoid leaving them concerned and making repeat visits to their GP to chase hospital appointments.
GPs in some cases were seeing patients 'multiple times' while they waited for hospital appointments, Dr Vautrey warned, and often ended up writing letters to demand urgent appointments for patients who needed to be seen quickly.
'This will carry on for weeks and months to be resolved,' he said - warning that in the meantime patients unable to access hospital services would continue to default to their GP.