A total of 41% of GPs said the capacity of their workforce had been significantly reduced by staff self-isolating during the COVID-19 outbreak, with a corresponding rise in workload.
A further 53% of GPs reported a slight reduction in workforce capacity and rise in workload due to staff self-isolating, with just 4% of 472 respondents to a BMA poll reporting no impact.
Doctors' leaders have called repeatedly for priority testing for frontline NHS staff to allow those self-isolating because they or family members have symptoms of COVID-19 to return to work rapidly if they are not infected.
But the poll found less than one in 10 GPs were always able to access testing for staff self-isolating with symptoms - and just 5% could access tests if they were self-isolating because a family member displayed symptoms.
The findings come just days after GPonline reported that around one in four GPs were thought to be self-isolating because they or a family member had shown coronavirus symptoms.
Health and social care secretary Matt Hancock has pledged to increase testing capacity to around 100,000 tests a day by the end of April - although it is not clear what proportion of these tests would be tests to show whether people are currently infected and what proportion tests to show previous infection.
The BMA poll findings came as more than 5,000 people have now been confirmed to have died in the UK after contracting COVID-19.
Five doctors dead
A fifth NHS doctor - heart surgeon Dr Jitendra Rathod - was confirmed to have died from coronavirus infection on 7 April. A 76-year-old Essex GP, Dr Habib Zaidi, last month became the first UK doctor confirmed to have died after being infected with coronavirus.
UK prime minister Boris Johnson, meanwhile, has been hospitalised with the virus and is currently in intensive care at St Thomas' Hospital in London.
The BMA poll also revealed chronic shortages of PPE for GPs and other NHS staff, with many unable to access protective kit recommended by Public Health England.
BMA chair Dr Chaand Nagpaul said it was 'frankly disgraceful that frontline staff are still expected to work unprotected'.
He said: 'We must protect doctors so they can protect patients. The government must get a grip on this situation now and give us cast iron assurances that each and every single doctor can be guaranteed access to PPE and be properly protected.'