An independent commissioner should be appointed to oversee police use of fingerprints, DNA and photographs of people taken into custody in Scotland, according to a watchdog.

HM Inspector of Constabulary in Scotland, Derek Penman, said such a move could deliver "truly independent oversight" of Police Scotland's use of biometrics.

The recommendation was one of several he put forward following an audit and review of Police Scotland's use of the facial search capabilities within the UK Police National Database (PND).

The inspector also called for ministers to strengthen the existing law and "close a potential legislative gap" surrounding the retention of images held by police.

HMICS was tasked with undertaking the review last year after UK Biometrics Commissioner Alastair MacGregor raised concerns about police forces using a computer which can match custody mugshots with faces trawled from CCTV images of crimes without a "proper and effective regulatory regime".

Police Scotland in May last year revealed that it has uploaded 601,837 mugshots of 334,594 Scots to the UK PND.

Outlining his findings, Mr Penman today concluded that Police Scotland has been "fully compliant with its own policy around the use of PND, and also with Home Office and College of Policing guidance".

He found that the Scottish force had conducted 567 facial searches on PND from March 28 2014 to July 8 2015. These 567 searches were of 330 different probe images obtained from crime or incident scenes.

He noted: "The number of facial searches conducted on PND by Police Scotland is equivalent to less than one search per day.

"Our audit found that each search by Police Scotland related to a specific crime, incident or inquiry and all uses by Police Scotland were lawful, proportionate and necessary."

But Mr Penman said his review did identify a need for improved legislation and better independent oversight around the police use of biometrics north of the border.

He said the Scottish Government should work with the force and other bodies to consider the establishment of an independent Scottish Commissioner "to address the issues of ethical and independent oversight over biometric databases and records held in Scotland".

Ministers should also work with police and the Scottish Police Authority to consider legislative provision over the retention and use of photographs by the police, he recommended, after finding there are no laws specific to the capture and use of photographs taken from people who are arrested and taken into police custody.

Mr Penman said: "The appointment of a Scottish Commissioner would provide independent and ethical oversight of the police use of all biometric data in accordance with the recommended code of practice and provide greater transparency and accountability.

"New and emerging technologies will increase the value and potential of biometric data and we believe that the introduction of a Code of Practice overseen by a Commissioner could safeguard and future-proof its use."

He added: "The existing legislation for police retention of biometric data primarily relates to fingerprints and DNA and not photographs.

"Although Police Scotland voluntarily applies the same policy for the retention of images as it does for fingerprints and DNA, there is an opportunity to close a potential legislative gap and provide greater clarity about the retention of images held by police and the purposes for which they may be used."