Three hundred civilian police jobs were today put officially "at risk" as Police Scotland announced it would axe half its control rooms.

Workers were this morning told that units handling 999 calls would close in Aberdeen, Dumfries, Glenrothes, Stirling and at the old Pitt Street HQ of Strathclyde Police.

Staff union Unison said the move would begin with the closure of the former control room of the old Dumfries and Galloway close as early as April or May with the loss of more than 30 posts.

The other four units, including the important Aberdeen centre, will be phased out over the next two years as the new single force seeks to deliver more than a £1bn in savings.

Gerry Crawley, of Unison, said: "We have deep concerns about the loss of jobs in Dumfries and Galloway and the other control rooms."

The Evening Times understands that 300 control room workers have already applied for voluntary redundancy but their applications were put on hold pending the "rationalistion", which had been widely flagged up by senior chiefs over the last year.

Although up to 300 posts have been put at risk, The Herald understands the actual figure to go is likely to be closer to 200. The losses should be delivered through voluntary redundancies, transfers and early retirements.

Within two years the entire police force will have four full-scale control rooms at Govan in Glasgow, Motherwell, Dundee and Bilston Glen near Edinburgh. A support control room will also be maintained in Inverness to cover the Highlands.

These will handle all 999 calls and major incidents.

However, only three of the units - Govan, Motherwell and Bilston Glen - will take calls under the new 101 non-emergency number. This means that all non-essential calls to the police in Scotland will be channeled to the central belt, source said.

"Workers are very upset, as you can imagine," said one insider as the news was broken this morning.

Mr Crawley also said that police chiefs were looking to change the ratio of officers to civilian staff in the control rooms.

"They are talking about it being close to 50-50," he said. "We find that completely unacceptable given that the costs of employing a police officer is much greater than an employee."

Unison has long argued that a decision to maintain police officer numbers means that civilian staff are bearing the brunt of cuts being brought under the single force.

Some 1000 people currently work in control rooms. They have long braced themselves for bad news.

Shortly before the single force started work last April, Chief Constable Sir Stephen House said that 10 control rooms were unlikely to be needed for a single force, suggesting three or four was a more likely number.

The Evening Times understands the functions of Pitt Street in Glasgow will be transferred to Govan and Motherwell. Stirling and Glenrothes will be merged in to Bilston Glen. And Aberdeen's work will go to Dundee.

Police Scotland declined to comment. It will publish its proposals in full this afternoon before putting them before a special meeting of its watchdog, the Scottish Police Authority, next week.

The SPA chairman, Vic Emery, said: "We recognise that this is a complex and sensitive proposal, which has long-term implications for the organisation of policing and the services engagement with local communities.

"Before taking a decision on whether this proposal is progressed, SPA members will ensure, through rigorous scrutiny in a public setting, that the rationale behind this proposal is well-evidenced, that the delivery plan is sound and that the outcome will deliver service benefits for all parts of Scotland."

Police Scotland today confirmed the changes affected ten control rooms and nine contact centres, currently spread over 11 sites, including a service centre Bucksburn in Aberdeen, which is also close.

Chief Superintendent Val Thomson, the officer in charge of the service, said: "The current structure across the 11 sites is based on the arrangements which were in place under the previous eight force structure in Scotland.

"Moving to fewer, larger centres will enhance our capability to respond to day today incidents, as well as complex and large scale emergencies, with increased availability of staff, better technology and easier and faster ways to share information."

"If approved, the move from eleven to five sites will be implemented over the next two years, with smaller locations that have less capacity and deal with fewer calls and incidents, closing.

"Those sites being retained will be expanded and modernised, with new ICT systems introduced to enable staff to use previous contact information to better identify a caller's needs and allow us to offer improved channels of communication."

Police Scotland stressed that the new changes would also involve substantial investment in digital technology - with insiders suggesting new staff would be needed to operate this.

Chief Supt Thomson said: "The changes will be introduced incrementally, allowing us to monitor each one closely and ensure that public service is not impacted on during the changes.

"Once complete, this change will improve the service our communities receive.

"Improvements in technologies will allow our staff to identify the location of an incident, and the nearest police resource, whether that is a local beat officer, a firearms officer or a specialist detective, using GPS technology."

Dumfries will close in April 2014; Stirling in December 2014; Glenrothes in March 2015; Pitt Street Glasgow in March 2015; and Aberdeen in December 2015.

Scottish Conservative justice spokeswoman Margaret Mitchell MSP said: "The closure of so many control rooms was never part of the plan for Police Scotland.

"The control rooms provide a valuable frontline resource to ensure incidents are dealt with as swiftly and efficiently as possible.

"But this valuable local knowledge would be lost if these proposals for centralisation of services go ahead.

"Civilian staff do a valuable job and will be understandably angry that these plans have emerged in the same week as senior officers have been awarded a £10,000 pay rise."