The leading players in the row over police centralisation squared up in public for the first time, with the head of the Scottish Police Services Authority being labelled a "messenger boy" for civil servants.

Yesterday members of the Strathclyde joint police board unanimously rejected moves to place any further police functions under the "SPSA umbrella" and any attempts to create a single national police force.

It was revealed that Strathclyde has still not signed off the service level agreement with the authority on Information Computer Technology (ICT), despite the fact the services were transferred on April 1.

The force has also refused to sign off on the quality of forensic science services, 11 months after they were transferred to the new support agency, referred to yesterday as the "state police services authority".

A report by the board's audit sub-committee said it is "deeply concerned at the potential for failure of service delivery by the SPSA in the future leading to a serious impact on the continuing provision of an effective police service in Strathclyde".

Councillor Barbara Grant suggested the board needed to go over the head of David Mulhern, chief executive of the SPSA, and call in senior civil servants to ask them to explain the accountability of the authority.

"Mr Mulhern is really only their message boy," she said. "What we need to have is the head of the justice department answering these questions."

Established under the Police, Public Order and Criminal Justice (Scotland) Act 2006, the SPSA was set up 12 months ago to produce efficiency savings by centralising the provision and procurement of training, IT and forensic services.

It also maintains the Scottish Crime and Drug Enforcement Agency (SCDEA), the country's leading crime fighting unit.

However, questions were raised about its efficiency last year when The Herald revealed that, unlike the police boards, it would not be VAT exempt and would incur extra charges of up to £5m a year.

Questions have also been raised about the interpretation of the legislation following the decision of Graeme Pearson, former head of the SCDEA, to take early retirement after complaints by politicians that the agency's autonomy had been compromised by the new authority.

Mr Mulhern yesterday explained that in relation to the procurement of ICT equipment, the authority might have found a way to avoid paying VAT but admitted that the authority paid VAT on its work last year.

"The preliminary response from HMRC was that they thought it was workable so we are quite hopeful," he said.Stephen House, the Chief Constable of Strathclyde, said: "We are looking at this in a positive manner and we are looking ahead rather than looking back to the quite torturous birth on the ICT side of it."On the question of police centralisation, Mervyn Rolfe, chair of the SPSA board, said: "SPSA is not actively seeking any expansion of services but we would be ready to accept any proposals by the Scottish Government, the forces, joint police boards and Cosla."