Scottish hospitals could save £6 million a year if they used locum doctors more efficiently, a public spending watchdog has said.

In 2008-09 health boards spent around £47 million on locum doctors, who cover other medics who are off sick or on holiday, or when posts are vacant.

The total is around double the amount spent in real terms in 1996-97.

Audit Scotland said money can be saved if those boards with the highest bills for locums reduced their costs to the national average.

Hourly rates for locum doctors vary from £11 to £104 depending on their grade, speciality and whether or not they work for an agency.

Every NHS board which spends more than the national average on locum doctors also have vacancy rates for consultants which are above the national average.

But the watchdog said it “may be difficult” for some health boards, especially those in rural and island areas, to reduce spending.

It added: “All NHS boards however should be capable of making savings on locum doctors by improving procurement procedures and, more generally, managing their workforce planning better to minimise demand for locum doctors.”

Robert Black, auditor general for Scotland, said: “Health boards need better information about why and when they use locum doctors, the grades, specialities of doctors they are hiring as locums and whether locum doctors are existing employees or from agencies.

“With better information boards could improve their workforce planning and use locum doctors more cost-effectively.”