Police Scotland is operating at minimum staffing levels for safety because "every penny is a prisoner", a tribunal has heard.

In a case where the force sexually discriminated against an officer, evidence revealed that the service is running at minimum safety levels due to budgetary constraints.

Police officers revealed that staffing is at "reactive levels" when the preference would be to operate at "proactive levels".

One senior officer also said that "any [cost] over and above" the basic requirement is considered "too much".

The case, which came on the back of cuts to officer and police staff numbers, involved former police officer Fiona Mair, a single mother who made a flexible working application to Police Scotland to allow her to look after her son.

Her application was refused as the hours she was requesting meant she would be an additional body on shift over and above the basic staffing level.

Ms Mair, who has since resigned from the force, went on to win her case for sex discrimination at an employment tribunal.

Employment judge Muriel Robison said Police Scotland's "slavish adherence" to basic staffing levels left little option but to refuse Ms Mair's application.

The judge added that the officer's request was a "relatively minor adjustment" to make in order to meet her needs as a single parent.

The tribunal heard that Ms Mair began her career as a police officer in 1990 with the then Strathclyde Police.

After her son was born she began working in case management at London Road police office in Glasgow, which allowed her to work from 8am to 4pm, Monday to Friday.

This suited her childcare arrangements as her son's father had moved to New Zealand.

However, in September 2014 she was told she was being moved to another unit which would require working different shift patterns.

It was at this point she submitted a flexible working application to allow her to start some shifts earlier so she could finish earlier to pick up her son.

The force refused this request but told her that she could choose to cut her hours to finish earlier.

Ms Mair explained that she could not afford to do this and eventually went on to resign from the force in October 2015.

The tribunal, which concluded in December last year, heard that staffing levels within the police are dictated by an Operational Base Level (OBL) which looks at the number of incidents likely to occur at certain time of the day, week or year and the number of officers needed to deal with those incidents.

Judge Robison said: "We heard evidence that the OBL was now essentially at reactive levels, that is the minimum level of staffing for safety, and although they strive to achieve proactive levels, budgetary constraints mean that is increasingly not possible."

Sergeant Jennie McFarlane, of the Scottish Police Federation, the organisation which represents rank and file officers, told the tribunal that the force "could rarely now operate at more than the reactive levels".

Superintendent Jim Coulbrough, of Greater Glasgow police, added that Ms Mair's application was refused on financial grounds because "every penny is a prisoner" for the force.

Police Scotland tried to argue that their decision was justified because it would have created a lack of "supervision and personal development" for Ms Mair.

However, Judge Robison said: "Overall, we were of the view that [Police Scotland] took a rigid mechanistic approach to the determination of the application by focusing too closely on... the information from the OBLs."

She added that had the force not discriminated against Ms Mair, "a long-serving police officer may not have required to resign".

David Kennedy, deputy general secretary of the Scottish Police Federation, said the equality commission was now working with police Scotland to try to improve flexible working practices. 

He added: "This isn't a new problem for police Scotland. I've been a police fed rep for years and this has been a long running problem, particularly for women.

"We know there is a stigma attached to making a flexible working application, people are afraid to make requests, and that has to change. 

"People usually make these applications because they need to, due to childcare or family commitments, and the force needs to recognise that. 

"This case was a good result and will hopefully change things for officers and the force for the better."

Police Scotland has suffered from budget problems since it was first created in 2013.

Hundreds of civilian staff were made redundant when the single force came into being and police officer numbers are now at a nine-year low.

The amount spent on overtime has also fallen each year since 2013.

Recent reports suggest the force is facing a £200 million funding gap over the next three years.

A Police Scotland spokeswoman said: "We note the decision of the tribunal from December 2017. Since then Police Scotland has been taking steps to implement actions based on the judgement."