UNIONS have been ejected from a meeting of Scotland's police watchdog in what one official called a "humiliation".

The Scottish Police Authority, which oversees the work of the national force, routinely allows staff to attend its closed sessions.

However, on Wednesday, without warning it excluded representatives of both staff union Unison and the Association of Scottish Police Superintendents (Asps) from a meeting in Edinburgh.

Insiders warned the move, the first of its kind, would hurt industrial relations as Unison and Asps counter substantial cuts in the force.

Unison regional organiser Gerry Crawley said: "We want to know why we were asked to leave and why there was no prior notification of this.

"We want to know what was being discussed that we were not supposed to hear. If we are not there, who is scrutinising the scrutinisers?"

The Unison official asked to go was heard to say she had suffered a "humiliation".

Unison has once before been asked not to attend a closed or private SPA session, which are not open to the general public or media.

This, The Herald understands, was because pay was being discussed. Unison had no objection to being excluded on that occasion.

However, staff associations including Asps and the Scottish Police Federation, which represents the force rank and file, have routinely attended close sessions.

Police Scotland and the SPA, until now, have sought to include such stakeholders at an early stage in discussion of sensitive issues, in return for a guarantee of confidentiality.

Chief Superintendent Niven Rennie, president of the Association Scottish Police Superintendents, was also asked to leave on Wednesday. He said this was "very surprising".

Mr Rennie added: "I don't want to sound over-sensitive about this.

"But Asps has a statutory role in ensuring effective and efficient policing and I am not aware of anything on the agenda of the closed sessions that would require use to be excluded."

The SPA, however, insisted that there was no blanket invitation for staff associations and unions to attend its closed sessions.

A spokeswoman said: "We conduct the vast majority of our business in public.

"On occasion, issues will arise which have an obligation of confidentiality attached to them and require to be considered in a closed session without third party or outside observers.

"Attendance at closed sessions has always been by invitation only and trade unions and staff associations have been invited to observe on a case by case basis."

Unison has been fighting a rearguard action against job losses since Police Scotland came in to being. Asps too has had gripes about the workload on its members and recently complained when a new assistance chief constable post was created.

Mr Crawley added his voice to that concern too.

He said: "We have the upmost respect for the individual involved, Val Thomson. But Police Scotland was created to achieve economies of scale and support staff have been decimated as a result. So to create another highly paid chief officer post is an absolute disgrace."

Chief Constable Sir Stephen House last month warned he would stand down next year. He also signalled what he called "extreme measures" would be needed to overcome a budget black hole of £11m in 2015-2016.