Speaking at a meeting of the Scottish Police Authority (SPA) on Thursday, Sir Iain Livingstone said the force would have to assess the sustainability of high levels of overtime.

It comes as a financial report put to the SPA projected there to be 452 fewer officers than previous budget assumptions had predicted.

And there is a risk of overtime increasing further to maintain service and operational levels if officer numbers continue to fall below forecast assumptions.

Overtime warning: Police Scotland Chief Constable Sir Iain Livingstone

Sir Iain previously raised concerns that officer numbers could continue to fall as a result of real-terms funding cuts of about £66 million.

The financial performance review, presented by James Gray, the SPA’s chief financial officer, predicted a first quarter being under budget of £2.3 million, largely due to the reduced officer numbers, which is saving more than £21 million.

However, against this underspend, there is an increase in police officer overtime, costing £11.9 million.

Addressing the overtime concerns, Sir Iain said: “We are seeing the impact in our service of having fewer officers across a range of operational areas including a responsiveness to calls from the public.

“Our forecast for the year shows we will run at an average of over 450 officers below our budgeted establishment of 17,134.

“We cannot continue to use overtime and place that burden on officers and staff of Police Scotland.”

Scottish police officers are to receive a 5% increase in their pay and allowances.

Using overtime to offset falling police numbers is unsustainable and cost £12 million, chief warns