A PROBE into an illegal spying operation linked to the unsolved murder of prostitute Emma Caldwell was held up for months over unexplained legal wrangling.

Police Scotland was unable to explain why emails between senior officers took three months to release, while contact details for retired officers were not handed to investigators for two months.

MSPs branded some of the hold-ups “absolutely staggering” as they quizzed senior police figures during a Holyrood committee.

They also blasted the force’s “overly secretive approach”, which led to heavily redacted reports which attempted to obscure information that was already in the public domain.

It comes after Durham Constabulary chief constable Michael Barton insisted Police Scotland prevented him from fully investigating illegal spying claims.

Scottish Liberal Democrat MSP Liam McArthur said: “I entirely understand and respect the requirement to redact reports of this nature, but it seems to me the extent of the redaction – including information that was in the public domain – spoke to an attitude that Mr Barton during his evidence session was moved to suggest was an overly secretive approach.”

Durham Constabulary was asked to probe Police Scotland’s Counter Corruption Unit (CCU) after it emerged officers had breached guidelines by attempting to uncover a journalist’s sources in relation to the murder of Ms Caldwell in 2005.

Under questioning from Tory MSP Margaret Mitchell, senior police officers repeatedly failed to explain delays in handing over information during the investigation.

Ms Mitchell said this “goes right to the heart of the criticism here – that the [police’s] legal department was risk averse, that is was not open and not transparent.”

She later dismissed an explanation by deputy chief constable Rose Fitzpatrick regarding what the police had learned from their failings.

She told the senior officer: “We’ve had these platitudes before DCC Fitzpatrick, with respect.”

Ms Mitchell added: “There was no criminality found. It was merely inept. And I’m afraid that’s what’s coming over today.”

Ms Fitzpatrick admitted the force had failed four colleagues at the centre of the probe into illegal surveillance.

But she defended Police Scotland’s handling of the independent investigation carried out by Mr Barton.

Ms Fitzpatrick said she had met with three of the four wronged officers in March of last year to offer a "wholehearted and unreserved" apology.

She said: "As I said to them when I met them and I have repeated in my letters to them, I feel we failed them as an organisation absolutely and that we continued to fail them by not being in contact with them and I continue to offer them my wholehearted apologies for that failing."

Mr Barton told the committee last month he had originally been asked to carry out an investigation into the CCU following a ruling of the Investigatory Powers Tribunal (IPT) but that was later downgraded to an inquiry.

Ms Fitzpatrick acknowledged there had been a "significant difference of professional view" between the two about how to proceed but that had been resolved by her taking legal advice.

She said: "It's not unusual in complex matters for there to be a difference of professional view about the best way of progressing things.

"But we were very clear that he and Durham Constabulary had been asked to undertake an independent investigation only into the complaints allegations, the non-criminal complaints allegations, and that our conduct regulations require other stages to take place should there require to be an investigation then into the conduct of individual officers."

Earlier this year an independent investigation into allegations of misconduct against officers in the former CCU, carried out by the Police Service of Northern Ireland, found there had been no misconduct.