Scotland's second-biggest police force failed to follow up properly a "significant" number of complaints against its officers, including accusations of criminal behaviour, instead filing them as "miscellaneous inquiries", the Police Complaints Commissioner for Scotland has found.
In an unprecedented examination of Lothian and Borders Police's complaint handling over a four-year period, Jim Martin found that 133 complaints had been misfiled in the lesser category, including 16 that would "reasonably be taken to allege criminality on the part of officers".
However, despite the seriousness of the latter allegations, in nine of the cases there is no evidence of any attempt to notify the area procurator-fiscal, who would decide whether to bring any prosecution, Mr Martin found.
The commissioner, whose post was introduced in April last year, also found evidence that the force had misled complainants, including an MP, as to how their grievances had been handled.
He has now asked L&B to reinvestigate all the original complaints, review its complaint-handling procedure and ensure that any relevant cases are referred to the fiscal.
The commission is also seeking an urgent meeting with the remainder of Scotland's eight police forces to ensure that official complaint-handling policies are being carried out properly.
Describing his findings as "very worrying", Mr Martin told The Herald: "What I have uncovered in this review is well over a hundred cases which haven't been handled according to correct procedures. The fact that some of the cases contain quite serious allegations is worrying.
"Whether it is a case of poor administration in some cases (or otherwise), is frankly neither here nor there. There are procedures in place to give the public confidence that their complaints are handled appropriately. That I found 133 cases of this not happening is very worrying."
The investigation into L&B's complaints and conduct department - the first time such an inquiry has taken place in Scotland - was sparked in May after Mr Martin found that officers had been "insensitive" in the handling of an apparent suicide of someone who had died in police custody.
The PCCS investigation, published today, looked at just over half of L&B's miscellaneous inquiry files (804) between 2003 and 2007 and found that 16.5% of those should have been filed as complaints.
This resulted in the official number of complaints against the force being under-reported by 7%, the report found.
Among the 16 complaints that could potentially give rise to criminal investigations were allegations of assault and verbal abuse against a child by police officers, dangerous driving and allegedly failing to tell one woman that her son had received hospital treatment after an altercation with police.
There were also allegations about evidence that was later given by officers in court but not recorded and where the fiscal appeared not to have been informed, the report found.
The review did not examine whether police officers had deliberately misfiled complaints. Mr Martin said this was a question for L&B to address and, if upheld, decide whether or not any disciplinary action was necessary.
However, a spokesman for the force sought to play down the findings, saying they had not found fault with actual complaint investigations.
The spokesman said there was no intention to take action against any officer as a result of the PCCS findings.
