Up to 95% of Scotland's GPs have opted out of providing 24-hour patient care, making the service unsustainable, a report suggests.
Under the new system, responsibility for out-of-hours care has shifted from GPs to NHS boards, and GPs can decide not to provide a 24 hour service.
The Audit Scotland report "primary care out-of-hours services" looks at how out-of-hours care has been managed and delivered since this change was implemented.
It shows that the number of doctors delivering out-of-hours services is steadily declining, particularly in rural areas.
The report suggests that NHS boards should invest in extending the roles of other health professionals, such as nurses and paramedics, and developing a new model of out-of-hours care.
Deputy Auditor General for Scotland Caroline Gardner said: "The way the service is currently delivered needs to change as there is a significant risk that it is unsustainable in its current form, particularly in Scotland and remote areas."
Dr Dean Marshall, chairman of the British Medical Association's Scottish General Practitioners Committee, said: "GPs agree that there needs to be improved communication and co-operation between the various branches of the NHS tasked with delivering primary care out-of-hours services.
"It seems that the government clearly did not appreciate the extent of the personal and financial burden bourne by GPs in delivering 24 hour patient care under old arrangements.
"BMA Scotland would welcome the opportunity to be involved in discussions on how the various service providers can work together to deliver out-of-hours care in the long term."