A top policeman has told MSPs he was "prevented" from carrying out a proper investigation into Police Scotland's Counter Corruption Unit (CCU).
Michael Barton, Chief Constable of Durham Constabulary, told Holyrood's Justice Sub-Committee on Policing the terms of reference for his inquiry left him "a little bit confused and a little bit concerned".
His force was asked by Police Scotland to probe the CCU after guidelines on accessing data were breached by officers attempting to uncover journalist sources in relation to the murder of Emma Caldwell in 2005.
Mr Barton told the committee he had originally been asked to carry out an investigation following a ruling of the Investigatory Powers Tribunal (IPT), meaning he would have access to all documents and be able to interview people under caution.
He said: "I was initially asked to conduct an investigation and that's what I agreed with (former Police Scotland Chief Constable) Phil Gormley.
"Subsequent to that, the professional standards department in Police Scotland decided that we should only conduct an inquiry. I argued with them all the way through.
"I should be allowed to do an investigation because that's the commitment that Police Scotland had given to the IPT and I was never allowed to do an investigation.
"So we were not allowed to have the investigation status which allows us to speak to officers who may or may not have been guilty of misconduct but (who it was) certainly pivotal for us to speak to under caution.
"As far as I was concerned I was asked to investigate and as far as I'm concerned... that's what the common man or woman would understand what an investigation is. That's what I wanted to do and I was prevented from doing so."
Mr Barton said he was frustrated by the decision and had he been allowed to carry out a proper investigation he could have brought an end to the matter "much sooner and much more effectively for the four complainants" who he said had been "gravely wronged".
He told MSPs: "I think currently the lawyers in Police Scotland are not transparent and they are overly defensive and they are risk adverse and it got in my way."
But he said he thought the issues were more a matter of "ineptitude" rather than conspiracy.
Last month an independent investigation into allegations of misconduct against officers in the former CCU, carried out by the Police Service of Northern Ireland (PSNI), found that there was no misconduct.
Speaking after the session Sub-Committee Convener John Finnie MSP said the evidence was "damning" and Police Scotland would be asked to respond.