The chief constable of an English force brought in to investigate a spying scandal has told MSPs that Police Scotland "prevented" him carrying out his work.
Durham Constabulary was asked to investigate after the Scottish force's Counter Corruption Unit (CCU) breached guidelines attempting to establish the source of media reports about failings during the inquiry into the unsolved murder of Emma Caldwell.
The English force was brought in after the Interception of Communications Commissioner’s Office (IOCCO) said Police Scotland had been “reckless” in failing to obtain judicial approval when trying to access communications data.
Appearing before MSPs on Holyrood's justice sub-committee on policing, Michael Barton said he had been prevented from speaking to officers under caution.
Mr Barton said the four complainants - two serving and two retired officers - in the case had been "gravely wronged" and he sought to correct information given to the committee by a senior Police Scotland officer, Assistant Chief Constable Alan Speirs, last year.
Mr Barton said he had initially been asked to investigate by Police Scotland's then chief constable, Phil Gormley.
"When I was given the inquiry it was very clear to me from the chief constable that we were being asked to do an investigation," Mr Barton told MSPs.
However, he said it later became clear that he was carrying out an inquiry - the distinction being that he was unable to question police officers under caution.
Mr Barton said he had argued with Police Scotland's professional standards department "all the way through" about being allowed to conduct a thorough investigation.
"That's what I wanted to do and I was prevented from doing so," he said.
It followed a probe carried out by Assistant Chief Constable Mark Hamilton, of the Police Service of Northern Ireland (PSNI), at the request of Police Scotland Deputy Chief Constable Rose Fitzpatrick following the Durham investigation.
Speaking after the meeting, committee convener John Finnie MSP, said: "We have heard damning evidence about Police Scotland's interaction with Durham Constabulary as they carried out vital investigations into the Counter Corruption Unit. We will be asking Police Scotland to respond at the Committee."
Labour MSP Daniel Johnson said: “The dysfunctional culture at the top of Police Scotland has been utterly exposed today.
"It has become clear that through sheer ineptitude and incompetence, Chief Constable Michael Barton was prevented from conducting a full inquiry into how the CCU handled the Emma Caldwell spying case.
“We already knew from his report that officers ‘dishonestly’ and ‘wilfully’ manipulated intelligence, that their requests to spy were ‘unlawful’ and based on ‘inaccurate’ information, and indeed were ‘a complete invention in all respects’.
“Now we know that he was unable to actually conduct the investigation he needed to, to get to the bottom of an incredibly serious misuse of police power.
“This will only serve to further undermine the already shaky public confidence in Police Scotland and depress the morale of hard-working rank and file officers.”
Deputy Chief Constable Rose Fitzpatrick said: "A full misconduct investigation was carried out by PSNI at our request, which is the element of the process that Chief Constable Barton says he was prevented from undertaking.
"The PSNI investigation found that there was no misconduct on the part of any of the seven officers who were investigated.
"It is our position, supported by external and independent legal opinion from a QC, that our regulations would not have permitted Chief Constable Barton from carrying out both the complaint inquiry and the misconduct investigation.
"We have previously said that there has been significant organisational learning from these inquiries and a report on this has been provided to the Scottish Parliament's justice sub-committee."