SCOTLAND'S most senior policemen claim that the age-old system of corroboration, where key evidence presented for criminal trial should be backed by two sources, no longer serves justice well.

The Association of Chief Police Officers Scotland (ACPOS) said scientific advances in investigation techniques had increased reliability of evidence with the quality of information more important than the quantity.

The comments are in response to the Carloway Review, which recommends the "archaic" rule of corroboration should be removed, and put police on a collision course with the legal establishment – from High Court judges to solicitors – who condemned the move.

Liberal Democrats want a Royal Commission on the proposals after Justice Secretary Kenny MacAskill said he was not minded to deviate from Lord Carloway's recommendation – or hold a further inquiry into the legal changes.

ACPOS argues there is no evidence to suggest Scotland, thought to be the only country in Europe to retain the principle of corroboration, has a lower or higher rate of miscarriages of justice as a result of corroboration.

It added: "While investigators should always seek to secure corroboration of facts in criminal investigations, ACPOS does not agree that the current Scottish system of rules of corroboration serves the interests of justice well."

ACPOS highlighted the point in the report that a single witness may be more persuasive than a "cloud of witnesses".

The Association of Scottish Police Superintendents said the necessity for every element of an inquiry or every item of evidence to be corroborated was "considered unnecessary in the modern criminal justice system".

A Scottish Government spokesman said all consultation responses would be carefully considered.