The current model of providing social work services in Scotland is unsustainable in the long-term, a report has found.

The Accounts Commission said the latest annual figure for social work spending is now £3.1bn, which is a 3% rise in real terms since 2011/12.

Local authorities are facing "significant challenges" to provide the services due to a range of financial pressures.

Audit Scotland, which prepared the report for the commission, forecast social work spending increasing by as much as £667m in the next five years unless new ways of delivering services are brought in.

The report states: "Current approaches to delivering social work services will not be sustainable in the long-term.

"Councils' social work departments are facing significant challenges because of a combination of financial pressures caused by a real-terms reduction in overall council spending, demographic change and the cost of implementing new legislation and policies.

"If councils and integration joint boards continue to provide services in the same way, we have estimated that these changes require councils' social work spending to increase by between £510 and £667m by 2020."

Around 70% of the 300,000 people helped through social work services in the latest figures were over 65.

The report estimates around 200,000 people work in the social care sector.

Commission chairman Douglas Sinclair said it is time for "hard choices" to be made on the future of the services.

Sinclair said: "Increasing pressures on social work and rising expectations of what it should deliver can only intensify.

"Now is the time for some frank discussions and hard choices. It is vital that people who use and provide services - and the wider public - are actively involved in that debate on future provision."

Scottish Labour called on the Scottish Government to "reflect" on its funding of local government.

The party's communities spokesman Alex Rowley said: "This expert report shows the human cost of the SNP cuts to councils.

"The fact that many pensioners are not getting the care they need is a clear demonstration of the failure of this SNP government to fund these vital services.

"The demand on social work services continues to grow whilst the budgets fall putting increasing pressure on staff.

"The SNP government must reflect on the cuts they are imposing on these services."

Responding to the report, Health Secretary Shona Robison said:"The integration of health and social care services is one of the most ambitious programmes of work that this government has undertaken and we have committed over half a billion pounds towards making the integration of services a success.

"Integration will support better provision of care within communities and in people's homes - helping people to lead longer, more independent lives."