Numbers of staff in primary care are 'moving further away from the government target of net growth of 5,000 more' full-time equivalent GPs by 2020, a report by the Health Foundation warns.
It highlights recent data showing that GP numbers are in decline - with a slight rise reported in August failing to cancel out a large decline highlighted in figures published at the end of 2016.
Meanwhile, numbers of managers employed in the NHS are now rising faster than any other major staff group, the think tank said - up 11% since 2015, but with overall numbers still 12% below 2010 levels.
The think tank report highlights government plans to recruit 2,000 GPs from outside the UK, but questions evidence to support the view that a programme offering £20,000 incentives for trainees in underdoctored areas will lead to a long-term rise in the workforce in those areas.
Two fifths of male GPs are aged 50 years or above, the report adds, and the rate at which this cohort leave the NHS could be accelerated by changes to pension rules. Meanwhile, numbers of women - who are more likely to work part-time - joining the profession are continuing to rise, meaning that 'the replacement number required is even greater', the report warns.
The report also highlights soaring pressure on GPs, with rising numbers of patients per full-time GP, morale at its lowest point since before the 2004 GP contract and stress at an all-time high.
Health secretary Jeremy Hunt has admitted failing adequately to prioritise building the GP workforce in his time as health secretary, but set out plans to address the problem at this year's RCGP conference.
BMA leaders have urged the government to commit to a long-term plan to give general practice the resources it needs.