POLICE Scotland faces a "considerable challenge" in closing an £11m funding gap this coming financial year, its finance chief has warned.

The national force has already found £46.5m of the £57.5m in savings it must make to break even in 2015-2016.

But it will - for the third year in a row - ask its ruling board, the Scottish Police Authority (SPA), to support an unbalanced budget for the next 12 months.

Janet Murray, the force's director of finance, has stressed the sheer difficulty identifying the final savings "principally" thanks to the SNP's commitment to maintaining officer numbers.

In a draft budget to go before the SPA on Tuesday, she hints at difficult decisions to come this year.

She said: "The delivery and timing of such cost reductions represents a considerable challenge to the authority and Police Scotland in terms of the options available for service delivery.

"Any such proposals will therefore require significant effort, political willingness and support and appetite for change."

The £11m cuts still to be made represent just one per cent of the force's roughly £1bn. Police Scotland is cutting its wage bill for civilian workers - much of the savings already identified thanks to voluntary redundancies and early retirements.

But the force has to replace officers who leave, meaning the biggest single item on its budget is off limits for cuts. That means the one per cent last savings must come from somewhere else.

Chief Superintendent Niven Rennie, president of the Association of Scottish Police Superintendents, said this was not tenable.

He said: "I am at a loss to suggest what they might want to cut; they have already cut to the bone.

"The government have set a figure of 17234 for police officers but it is very hard to square their budget with that figure. If you want that many cops, you must provide the budget to go with it.

"They have already cut the car fleet - we have heard of an officer trying to go by bus to a call.

"They have cut admin and they are letting civilian workers go - meaning some of their jobs have to be backfilled by police."

Mr Rennie, however, did not think major investigations would suffer in cuts - with serious crime, he said, still prioritised.

The SPA has previously passed two other unbalanced budgets with the force managing to make savings "in year".

Police Scotland ended 2014-2015 with a balanced budget, despite starting off without one.

But SPA's own financial watchdog, Amy McDonald, in another paper to Tuesday's meeting suggested this financial year would be harder.

She wrote: Much of the duplication from having nine individual police

organisations has already been removed, and the efficiencies of having combined functions have been realised.

"Achieving a balanced budget in the 2015/16 year is therefore a considerably more difficult and stretching target."

Ms McDonald said SPA and its members would have to take detailed control of how the budget progressed this financial year.

A Scottish Government spokesman said: "Clearly, it is for SPA and Police Scotland to determine the best possible use of the budget according to national and local priorities and one of the benefits of police reform is that all parts of Scotland now have access to specialist equipment and expertise whenever and wherever it is needed."

Savings already identified for 20145-2016 include a cut in rent allowance for officers of £1m as the benefit is phased out and a drop of £1m in fuel costs as prices drop.

The bulk of revenue savings, however, comes from ongoing rationalisation under the single force, including £4m of excess buildings closing.