BMA estimates suggest up to 16,000 general practice staff could be off work with COVID-19 by Christmas Day in England - stripping nearly three people from each practice on average.
A huge surge in infections has seen more than 615,000 confirmed COVID-19 cases reported UK-wide in the past seven days alone - and practices are reporting problems with maintaining services.
GPonline reported this week that one practice was forced to warn patients that telephone access may take longer than usual because half its reception staff were off work with COVID-19 infections, while another had to close one of the sites it operates from and others said services would be reduced faster than expected.
GP leaders say signs that practices and other NHS services are struggling must act as a 'canary in the mine' that alerts ministers to the need for a rapid expansion of measures to control the spread of COVID-19 - such as a return to social distancing measures and more restrictions on large indoor gatherings.
They warned that failure to take action now risks compromising the accelerated booster campaign - which has seen GP-led sites deliver millions of doses of vaccine in recent days - and ultimately could lead to the 'NHS being overwhelmed'. However, the latest call for measures to be stepped up came as prime minister Boris Johnson announced that no new restrictions would come in before Christmas.
NHS England has told practices to consider pausing routine and non-urgent work to focus on the vaccination campaign and to redeploy staff to support the rollout of jabs, while temporary changes to the GP contract have been brought in to ease pressure on practices.
But GP leaders said signs that practices are struggling show that increased measures to limit the spread of the highly transmissible Omicron variant - which the government has said will drive a 'tidal wave' of infections - are vital.
BMA GP committee chair for England Dr Farah Jameel said: 'The reduction of some GP services or even temporary closure of surgeries due to staff sickness from COVID-19 is incredibly worrying and yet another reason why we need to see more measures from government to contain the spread of Omicron now.
'Without a fully-functioning general practice system, patients won’t be able to get the care they need in the community, leaving them with no choice but to seek help from other parts of the system instead, further risking the NHS becoming overwhelmed.
'GPs and their teams are also at the forefront of the booster campaign, and this too will be seriously compromised if we don’t have the staff on the ground to deliver jabs.
'The impact of Omicron infections on staffing pressures across the NHS is the canary in the mine, and should be a wake-up call to government that more needs to be done, right now, to halt the spread of this virus.
'GPs and their teams also need adequate PPE supplies and access to suitable premises that can meet IPC guidelines, so as to reduce the risk of transmission among patients and staff. Fundamentally, the public must be encouraged to get tested if they think they have any symptoms of COVID-19. If government fails to act, it’s not just general practice that will cease to function, but the entire NHS.'