A further one in five practices say they have been able to recruit, but only after a three- to six-month wait, according to the BMA poll of 3,567 GP partners.
The findings reveal the scale of the recruitment crisis facing the profession, and come just a week after the BMA revealed data showing that eight out of 10 GPs face unmanageable workload.
Soaring workload is closely linked to practices' inability fill vacancies, the BMA warned. A total of 44% of partners who reported that their workload was excessive and significantly impacting on their ability to provide high quality, safe patient care reported being unable to fill GP vacancies in the past 12 months.
Meanwhile, nearly a third of partners who said their practice uses GP locums said they did so to cover long-term workforce gaps.
GPC chair Dr Chaand Nagpaul said: 'It is deeply concerning that so many GPs are reporting that their practices effectively have permanent holes in their workforce, which they are unable to fill.
'In addition to this, only a small number of GP practices are operating with no vacancies, while the vast majority of GP services are suffering from constant shortages of GPs. It is clear that the crisis is so bad that general practice is being kept afloat by the essential help of locums who are stepping in to provide day-to-day services to patients.
'These chronic shortages come despite government promises at the last election to recruit 5,000 more GPs, a pledge that has failed to materialise. As these figures demonstrate, those practices with long-term vacancies are also those struggling with unmanageable workload, leaving many GP services struggling to provide even basic care to their community.
'We need ministers to listen to the warnings from grassroots GPs and implement in full their pledges in the GP Forward View to properly staff and resource general practice. While NHS England has accepted the BMA’s recommendations from our Urgent Prescription for General Practice we now need words turned in to swift action to rapidly turn around this current crisis in GP services.'
GPonline reported earlier this month that practices serving 5m patients could be forced to close in the next 12 months, with one in 10 GPs warning their practice could face closure in the coming year due to funding problems.
Polling by this website also suggested that around half of existing vacancies for GP partnership roles had been unfilled for a year or more.