Fresh allegations have been raised against Police Scotland's counter-corruption unit, including a claim of officers attempting to pervert the course of justice.

Counter corruption officers have faced 25 complaints in the last seven years, including criminal allegations, according to the head of Police Scotland.

Speaking to Holyrood's Justice Committee on Wednesday, chief constable Phil Gormley also revealed allegations that members of the squad had twice breached data protection laws, although no further action was taken.

The most recent complaint includes the allegation that an officer attempted to pervert the course of justice, along with 11 further non-criminal allegations.

Within the 25 total complaints against officers in the unit since 2009 are 108 separate allegations.

Mr Gormley told MSPs previous complaints have either resulted in no action being taken or officers being given "corrective advice".

In a letter to the committee, he said: "I would like to take this opportunity to inform the committee that a further complaint made by a member of Police Scotland about the counter corruption unit within the above time period has been identified.

"This was not confirmed or recorded until after the correspondence to you dated June 30 2016 and as such was not 'returned' in the original search.

"The complaint includes one criminal allegation of an attempt to pervert the course of justice and 11 non-criminal allegations. This is currently the subject of investigation."

The chief constable had been asked to detail criminal complaints made against members of the CCU carrying out their duties by Margaret Mitchell, convener of the Justice Committee.

He revealed that 17 misconduct allegations had been made against officers in the unit in relation to their duties since 2009.

In his letter, Mr Gormley added: "For completeness, the total number of complaints within this time period is 25 and the total number of allegations is 108.

"I have asked the chief constable of Durham Constabulary, chief constable Mike Barton, to undertake a review of complaints made against staff in Police Scotland's counter corruption unit."

He also noted that many of the allegations were made before the establishment of Police Scotland and relate to "legacy" regional forces.

Mr Barton of Durham Constabulary is already leading an independent review into a breach of guidelines by the CCU when it accessed data without consent while trying to learn more about a journalist's sources in relation to the case of murdered prostitute Emma Caldwell.

In a report in June, HM Inspector of Constabulary in Scotland (HMICS) Derek Penman made 39 recommendations for improvements after investigating the unit.

A spokesman for the Scottish Police Authority (SPA) said: "We recognise the ongoing public and parliamentary interests in this area of policing, but it is important to recognise the progress already made since HMICS delivered its report on the counter-corruption unit in June.

"Police Scotland has subsequently announced an independent review by Durham Police which is due to report later this year.

"Taken together, the insight from the HMICS report, the work already undertaken by the new Police Scotland leadership team and the review now under way all provide a clear path for the service to drive improvement and rebuild both workforce and public confidence.

"The fact that we now have a reference group involving representatives from the SPA, Crown Office and Procurator Fiscal Service, Association of Scottish Police Superintendents, Scottish Police Federation and British Transport Police, as well as solicitors with experience in the area, has sent a powerful signal of the changing approach.

"That has been set up to review Police Scotland's progress in the implementation of HMICS's recommendations and seeks to ensure that this is done within reasonable time-scales."

Scottish Conservative shadow justice secretary Douglas Ross said: "These are extremely concerning developments in a story that has already raised difficult questions for Police Scotland.

"People will find it particularly troubling that the unit tasked with cracking down on corruption is facing allegations of this kind.

"Trust in the single force among the public is brittle thanks to a range of negative stories over the last couple of years, and these further reports will do nothing to help that."

Liberal Democrat MSP Liam McArthur commented that the CCU had been "in the eye of the storm over attempts to hack journalistic sources".

He said: "This letter reveals more than 130 complaints and allegations about the conduct of CCU officers and criminal investigations into allegations of perverting the course of justice.

"Reports like this can only undermine the good work of police officers across Scotland. It looks like some officers within this unit thought that the rules did not apply to them.

"Independent scrutiny is required to ensure that we get the answers we need."