Scotland's biggest police force was last night rapped for holding a 14-year-old boy in adult cells for more than two days.

Police Complaints Commissioner Jim Martin, in his first major announcement, last night called on Strathclyde Police to apologise to the youth and his mother after an incident he said pointed to a "systemic failure" in the way the force detained children.

The boy - identified as X - was locked up for 59 hours last year in two separate police stations after he was found carrying a knife and drunk at 2.30 on a Saturday morning in September 2006.

His mother, who was not immediately told of his detention, made 16 complaints against the police, seven of which Mr Martin upheld after a painstaking four-month investigation.

Mr Martin said: "It is of significant concern that, in considering the overall complaint, Strathclyde Police failed to identify and take steps to correct what appears to be a systemic failure in relation to the detention in custody of children.

"It is clear to me that various Strathclyde Police officers of various levels of seniority, were operating with an incorrect understanding of the force's standard operating procedures relating to the detention in custody of children."

Mr Martin, a former senior teaching union official, last night made it clear that he will be a robust and independent arbiter for police complaints.

He called on the Chief Inspector of Constabularies to look at his concerns with Strathclyde's conduct over the child's detention. The Herald understands child X may not be the only individual under 16 detained in breach of Strathclyde's own rules.

Senior officers at Strathclyde were late yesterday still digesting Mr Martin's findings and unable to comment.