NHS England has told GP practices they could lose more than £40,000 a year in funding if they close during core hours, as part of a drive to end 'routine half-day surgery closures'.
Officials have estimated that forcing around one in 10 GP practices that close for part of the week during core hours to remain open could create 'up to 287,000 GP appointments a year'.
But BMA GP committee chair Dr Richard Vautrey accused NHS England of coming up with 'fantasy figures' - warning that forcing practices to offer more appointments during core hours could simply drive down their ability to offer access at evenings and weekends.
GP opening times
He said: 'It is disingenuous for NHS England to be so categorical in claiming they know exactly how many more appointments would be available if practices changed their opening arrangements.
'The potential impact of these changes must be considered - for instance GPs may no longer be able to do evening or weekend appointments because of additional commitments during the day.
'Every GP practice wants to be able deliver the best for their communities in the 21st century but with significant workforce shortages, and a failure of NHS England to invest in much needed premises and IT infrastructure, it has left GPs under greater pressure than ever before.
'And so instead of coming up with fantasy figures and threatening GPs with reduced funding, NHS leaders must work to address the ongoing recruitment and retention crisis to bring about lasting improvement to patient care and avoid putting overworked doctors under further strain.'
RCGP chair Professor Helen Stokes-Lampard added: 'GPs and our teams are working under intense resource and workforce pressures - and it is disingenuous to insinuate that we are in some way shirking our responsibilities to patients.'
The RCGP chair pointed out that when practices close during core hours it is 'not time lost to patients, it is usually time spent conducting telephone or online consultations, or making home visits - or some of the other many vital tasks that GPs and our teams are required to do, such as complying with mandatory or statutory training'.
She added: 'It is also more likely that it is branch practices that are affiliated to larger sites that have regular closing hours - or very small practices that are forced to close due to staffing shortages. In either case, adequate cover arrangements will always be put in place for patients who need urgent care and, wherever possible, patients are fully informed well in advance, and explanatory messages are posted on websites and surgery answer machines.'
NHS England acting director of primary care Dr Nikita Kanani has backed plans to boost available appointments by ending half-day closures.
She said: 'Family doctors are the bedrock of our health service and access to GP practices remains essential to the NHS as we deliver our long-term plan and also to patients who want GPs to be available at core times, as well as in the evenings and at weekends. By curbing half-day closures we will be freeing up hundreds of thousands of appointments at a time when we know it can sometimes be tricky to see your GP.'