Police Scotland's most senior officer has urged the SNP to give him the gift of flexibility for Christmas by reviewing its manifesto pledge to maintain 1,000 extra police officers.

Deputy chief constable Neil Richardson, a candidate to be the next chief constable following Sir Stephen House's formal retirement, said the debate about Police Scotland's future needs to move on from personnel numbers to finding an appropriate budget.

The force is still struggling to bridge its £25 million shortfall - equivalent to the cost of nearly 700 police officers - by the end of the financial year, Holyrood's Justice Committee heard.

Mr Richardson confirmed police officers are "backfilling" jobs previously done by support staff and said further staff cuts are expected.

Former policeman John Finnie MSP, who resigned from the SNP 18 months after the 2011 Scottish election, said the SNP manifesto pledge he was elected on is effectively not being fulfilled as officers are replacing lost staff.

Mr Richardson said the pledge was helpful in the initial stages of police reform, as it focussed minds on cutting other budget lines and protected officers from the redundancies seen in England and Wales, but he said the budget is now more important than police numbers.

Committee convener Christine Grahame, an SNP MSP, said: "If Father Christmas was to bring you a present, would it be that you don't have to stick with 17,234 police officers so you could have some flexibility with the civilian balance?"

Mr Richardson said: "I absolutely want as much flexibility as I can. I think the debate is in the wrong place.

"The numbers part is less important than the money part, and I'm more interested in what settlement I can secure and from that how best to deliver the necessary policing services across Scotland."

He added: "The issue about numbers has become quite unhelpful and sets in the minds of community members that the measure of success is how many police officers are permanently deployed.

"That is difficult when it is directly against the model that we are trying to deliver, which is if there is a need that need will be met."

He said the Scottish Government's comprehensive spending review "will undoubtedly drive another opportunity for us to determine what service we are required to deliver across Scotland, and therefore what mix of staff and officers we need".

He said the manifesto pledge had "actually been quite helpful over the initial stages of reform to ensure that the focus was on the more longer term and challenging areas".

He added: "It has enabled us to keep a critical mass of police officers to ensure that service delivery is sustained.

"The contrast is absolutely stark if you look south of the border, where you have seen dramatic reductions in officer numbers."

He added: "The reality is we do need to find a balanced workforce... and you have to find what is the best asset that you need to bring in. Is it support staff, or is it a warranted officer?"

Mr Finnie said: "I stood on a platform for a party with a manifesto commitment for 1,000 extra officers. The intention was to provide the effect of 1,000 extra officers.

"With the consummate loss of police support staff that's not possible, not least because some of these 1,000 officers are now replacing them."

Mr Richardson said "there is no policy on wholesale backfilling" but he confirmed it is happening.

"We are living in a world where savings have to made and it would be wrong for me to say there won't be further reductions in staff," he said. "What I can't say at the moment is the numbers involved.

"We are actively working through plans to look at how we can best balance the budget.

"Depending on what the settlement looks like, when that becomes apparent we will be in a better position to determine what the size and scale of the organisation needs to be.

"As we seek to improve efficiency, it releases or provides the opportunity to release at least, potentially staff that are no longer required because the system is far more efficient and this is something that we have been working with the staff and the unions on."

The Scottish Government is also keeping pressure on the UK Government to restore the VAT exemption enjoyed by Scotland's eight legacy police forces.

Janet Murray, director of financial services at Police Scotland, said: "The irrecoverable figure from VAT is now in the region of £33 million... which would be in the region of 900 officers."