A SENIOR police officer who led Police Scotland's Human Trafficking Unit has been demoted three ranks after allegedly making a sectarian comment.

Ruth Gilfillan has fallen from detective chief inspector to constable following an internal probe into a remark she made at work.

However, a spokesperson for the Scottish Police Federation, which is representing her, said she is appealing the decision.

Gilfillan worked in the old Strathclyde force before taking a senior role in Police Scotland’s National Rape Taskforce and Human Trafficking Unit. She appeared in a hard-hitting Channel 4 documentary, Modern British Slavery, as an officer carrying out a spot check on a nail bar in Glasgow.

Gilfillan also had a role in defending the controversial police raids on Edinburgh saunas, which had operated as brothels with the consent of local authorities since the 1980s.

She said in 2014: “This is categorically not about criminalising sex workers and it’s factually inaccurate to claim otherwise.

“The visits would involve a support worker with a police officer and the main aim is to improve welfare and build trust. The whole concept is built around consultation with partners about the feasibility of the approach and the consent of the individuals being visited.”

However, it was reported in 2015 that Gilfillan had been arrested at work after allegedly using sectarian language during an argument with a colleague.

The allegations reportedly related to remarks she made after she saw a Celtic birthday cake that a male detective had brought in for a relative.

The procurator fiscal dropped the case, but Police Scotland embarked on a misconduct investigation and completed the inquiry recently.

Sources said the disciplinary action taken was a demotion to constable, which could cost Gilfillan tens of thousands of pounds in pay and pension.

Graeme Pearson, the former head of the Scottish Crime and Drug Enforcement Agency, said: “The penalty is very unusual and reflects the attitudes the Police Scotland Executive has towards such incidents. This will show that the force is taking these matters very seriously.”

John Finnie MSP, the Justice spokesperson for the Scottish Greens, said: “It’s right that an appeal process is in place and I’m confident the panel will carefully consider whether a demotion was the correct punishment for this offence. I know that Police Scotland will want to be seen to be countering any notion that sectarianism is allowed to go on unchallenged and unpunished within the force.”

Dave Scott, the director of the anti-sectarianism charity Nil by Mouth, said: “We enjoy a very strong relationship with the British Transport Police and have provided regular training to officers since 2011. This was very much driven by senior officers with strong, clear decisive leadership shown. It’s much patchier with Police Scotland as we have some excellent joint engagement in Lanarkshire schools but little involvement elsewhere. We would be more than happy to assist the force in constructively dealing with any internal issues if invited to do so.”

An SPF spokesman said: “The officer will be appealing the decision.”

A spokesperson for Police Scotland said: "This matter remains a live internal conduct process and as such it would be inappropriate for us to comment further."

Asked if Gilfillan wanted to comment, the spokesperson said: “We are not making any further statement on this matter.”