Challenges facing the NHS in Scotland include rising vacancy rates, increased agency costs and an ageing workforce, auditors have warned.

A briefing from Audit Scotland in advance of a series of reports on the health service workforce shows staff numbers are at their highest ever level, up 5% since 2012.

Despite this, vacancy rates for consultants, allied health professionals and nurses and midwives have increased over the period.

The consultant vacancy rate sat at 6.5% in 2016, with general practice at 5%.

Meanwhile, the percentage of staff spending on agency employees increased between 2011/12 and 2015/16 from 1.4% to 2.8%, hitting £175 million.

Auditors also highlighted a trend towards an older workforce with 38% of staff aged over 50 in 2016, compared with 34% in 2012.

Turnover and sickness absence rates have also increased slightly over the last few years.

Labour health spokesman Anas Sarwar MSP accused the Scottish Government of presiding over a "workforce crisis".

He said: "It was Nicola Sturgeon as health secretary who slashed training places for nurses and midwives and our health service is now in real trouble as a result."

Tory health spokesman Donald Cameron MSP said: "The SNP has been in sole charge of health for a decade, and these failings are entirely its responsibility.

"It hasn't sufficiently staffed wards, has the wrong priorities and has failed to train enough nurses."

Liberal Democrat health spokesman Alex Cole-Hamilton MSP described the Government's record on workforce planning as "woeful".

He added: "It takes seven years to train a doctor but staffing levels are only being planned five years ahead.

"The Health Secretary needs to immediately explain to patients and under pressure staff how her new strategy will end this workforce crisis."

Health Secretary Shona Robison said: "Under this Government, NHS staff numbers have risen to record highs - with more consultants, nurses and midwives now delivering care for the people of Scotland.

"There are now 11,500 more staff working in our NHS, with nearly 1,000 of these recruited in the last year. In the last 10 years we've also seen a 46% increase in consultants. These extra staff will ensure people all across Scotland get the high-quality NHS services that they rightly expect.

"We are also committed to preparing our NHS workforce, with a five-year consecutive increase in the number of student nursing and midwifery places. We're also committed to keeping the nurse student bursary and free tuition - unlike the UK Government who have scrapped both in England. The latest figures show there were almost 10,000 nurses and midwives in training in 2015.

"We also recently published a discussion document on national health and social care workforce planning, seeking the views of individuals and organisations within our NHS and social care services to ensure we have the right skills mix for the future."