The Scottish government pledged in 2017 to recruit an extra 800 GPs - increasing Scotland's 4,398 headcount GPs to 5,198 by 2027.
But an Audit Scotland report has projected that despite a recruitment drive, the total GP workforce is on track to reach just 4,417 GPs by 2027 - almost unchanged from the current figure.
In addition, the watchdog warns, with more GPs working part-time, any increase in headcount doctors is likely to translate into 'considerably less' in terms of the full-time equivalent workforce.
Audit Scotland suggests the government will fall short of its 800-GP target because of several factors - with a projected 662 of the shortfall attributed to 'joiner and leaver trends', 90 to changing workforce patterns and 30 to a reduction in the workforce triggered by plans to leave the EU.
The report highlights that one in three GPs in Scotland are aged over 50, that numbers of GP partners are falling in line with the trend in England, and points to the impact of heavy taxation on pensions that has pushed many doctors to reduce working hours or consider stopping work.
Despite the pledge to recruit an extra 800 GPs by 2027, the Scottish government's efforts to develop workforce planning have been 'slow', the report warns.
Auditor general for Scotland Caroline Gardner said: 'Scotland's primary care workforce is under pressure and operating in an uncertain climate. That makes detailed planning for the future even more important.
'To date, the Scottish government has introduced major policy changes without a reliable basis for its plans. It now needs to get a much clearer picture of the workforce and set out detailed plans addressing how its initiatives will improve patient care and deal with future demand on services.'
BMA Scottish GP committee deputy chair Dr Andrew Cowie said: 'Today’s report from Audit Scotland highlights the work that still needs to be done to make general practice a more attractive career option for doctors.
'It is no secret that Scotland desperately needs more doctors in general practice, and with not enough doctors choosing this as a career path, and more senior doctors retiring early or cutting down their working hours, it is difficult to see how the Scottish government is going to meet its target of an additional 800 GPs to the current workforce.'
He said the new GP contract introduced in Scotland in 2018 had set general practice 'on the right direction of travel and offers the best hope for sustainable general practice'.
Dr Cowie added: 'I understand the concerns raised by our rural GPs, who are facing major recruitment and retention issues and a real struggle to get locums and replacements in some of the most remote communities. Our approach to rural areas does need to be flexible and we all need to keep working on appropriate solutions.
'The core aim of the contract was – and remains – to restore hope to the profession and make becoming a GP an attractive career choice for young doctors, by lessening some of the burdens such as inappropriate excessive workloads, responsibility for employing a large practice-based team, and the risks associated with owning practice premises. Only then will we start to see an increase in the number of GPs in Scotland, and the future of primary care improved.'
Scottish health secretary Jeane Freeman said: 'The new GP contract and investment in multi-disciplinary teams is increasing capacity in primary care and helping patients to be seen at the right time by the right person. It will also help reduce GP workload, making the career even more attractive to new doctors.
'We are also taking action to build a workforce that can meet increasing demand. For 2019/20 we’ve increased nursing and midwifery student intakes by 7.6% - an extra 283 places. By 2020/21 we will have increased medical school places by 22% over 2016 levels, equivalent to an extra 190 places.
'Uncertainty around a "no deal" Brexit continues to pose a significant threat across the health and social care sector, both in terms of the supply of medicines and critical goods and the impact which the loss of freedom of movement will have on the recruitment and retention of staff.'