A Scottish police force failed to investigate a claim that some of its officers were influenced by the Freemasons, the Police Complaints Commissioner for Scotland rules today.

The finding by Jim Martin relates to a long-running case involving two members of the public and Northern Constabulary.

One man, named only as Mr A in the commissioner's report, made an accusation of threatening behaviour against another man. Mr A was said to have requested that no formal police action be taken, but that the police speak to him about the incident.

A sergeant and constable visited the second man, but he subsequently claimed that they had not been interested in what he had to say. He believed they were working to Mr A's agenda, due to the influence of an external organisation. The Freemasons are not named in Mr Martin's report, but are believed to be the group involved.

He rules today that Northern Constabulary failed to handle in an acceptable manner allegations made about an individual officer and a part of the force being influenced by an external organisation.

"I have real concerns about the professional precision and seriousness with which the complaint was handled throughout.

"It is circumstances such as these that can cause disquiet about police investigating complaints about the police. I believe Northern Constabulary should now investigate the complainer's concerns in a more professional manner."

Mr Martin said that, had the force initially placed greater emphasis on engaging with the complainer in order to solve these issues, it may have been possible either to satisfy or dispose of the complainer's concerns at an earlier juncture.

He rejected the complaint that the police failed to consider the complainer's views when they first visited his home on November 14, 2006, but said there did not appear to have been a proper investigation into the second complaint, that Northern Constabulary was influenced by an external organisation, and had not treated the complaint seriously.

The complaint was originally investigated by an inspector who requested that a copy of her report be forwarded to the area procurator-fiscal as the allegation against Sergeant B was serious and could be considered criminal. Instead, Chief Inspector F instructed a sergeant to review the report.

The man at the centre of the row also alleged he was stopped a number of times after the first incident and believed that this was as a result of Mr A's complaint and this was upheld.

A spokesman for Northern Constabulary said they would have to study the report before commenting.

In August, Mr Martin found that Lothian and Borders Police had failed to follow up properly a "significant" number of complaints against its officers. Over a four-year period, Mr Martin found 133 complaints had been misfiled as "miscellaneous inquiries".