The National Health Service in Scotland loses about �10m every year because thousands of people fail to turn up for outpatient clinic appointments, according to a report.

The research, from Audit Scotland, also reveals service improvements for those patients who do keep their appointments are difficult because of a lack of centrally collected information.

Robert Black, Scotland's auditor general, has called for a comprehensive review of the whole system.

Last year, 161,000 Scots failed to turn up for appointments at outpatient clinics.

Non-attendance is a widespread problem and each missed appointment is estimated to cost �63, helping the total bill to over �10m annually.

Outpatient clinics are often double-booked because staff know about 12% of new patients will not turn up.

'Few records'

However, the practice of double-booking can lead to long waits and overloaded doctors and nurses when patients do appear.

According to Audit Scotland, there can be other problems for those patients who do turn up.

It is not mandatory to record how outpatients are dealt with - and few trusts do, it said.

Information on treatments being used and their outcome is patchy and not always reliable.

Continuity of care may be crucial, but with no national data collected, there is no way to monitor how outpatients are treated across the country.

That lack of information, said Audit Scotland, is making it difficult to improve services, prompting Mr Black to call for a shake-up of the system.