Cutting sickness rates could give councils across Scotland a staffing boost equivalent to taking on about 650 full-time workers, a new report claims.

Local authority staff numbers have fallen by 7% over the last five years - the equivalent of 15,100 full-time posts - and most councils have had to cut their workforces.

Public spending watchdogs at the Accounts Commission highlighted staff sickness rates over 2015/16.

These varied from an average of 8.8 days off a year as a result of illness for non-teaching staff in Aberdeenshire to an average of 14.8 days in the Western Isles.

The commission's report said: "If councils with high absence levels could reduce these to be in line with the top eight performing councils they would gain the equivalent staff time of about 650 full-time employees across Scotland."

Funding from the Scottish Government has been reduced by 9.2% in real terms since 2010-11, the Accounts Commission reported.

It said authorities had "faced significant challenges from a long-term decline in revenue funding and from an ageing and growing population", adding "the scale of these challenges continues to grow".

The report said: "Councils are responding to the challenges by continuing to adopt alternative ways of working, reducing the level of service they provide and reviewing fees and charges.

"While some councils are making good progress in managing services and delivering savings, others are not.

"The pace and scale of reform needs to increase in some councils. Despite these challenges, councils' performance has been maintained or improved."

It also warned: "With reducing budgets and workforces, councils will find delivering improvements increasingly difficult.

"It is critical, therefore, that they set clear long-term strategies and plans that target effort on priority areas."

With local government elections taking place in May, the report said: "The next council term is likely to bring significant challenges and uncertainties for councils."

Councils approved £524m of savings in 2016/17 and set out plans to use £79m from reserves to balance their budgets.

The report said: "We estimated that councils would have funding gaps of £358m in 2017/18 and £544m in 2018/19.

"These figures are likely to change as councils approve their 2017/18 budgets and continue to identify and deliver savings.

"However, they do demonstrate the scale of the challenge facing councils."