A police chief arrested over allegations of corruption is suing the heads of three police forces and the boss of the National Crime Agency (NCA).
Chief constable of Cleveland Sean Price and his deputy Derek Bonnard were arrested last August and held on suspicion of misconduct in a public office, fraud by abuse of position, and corrupt practice.
Both men are taking the civil action, claiming unlawful arrest, false imprisonment and trespass, their lawyers said.
Rebian Solicitors served letters before claim today on Keith Bristow, the interim director general of the NCA and former chief of Warwickshire Police, the chief constables of North Yorkshire, Warwickshire and West Yorkshire, and the two officers who arrested Mr Price and Mr Bonnard.
A statement said: "The claims for unlawful arrest, false imprisonment and trespass to property and goods arise out of the arrest and detention of the two officers on August 3 2011."
The criminal investigation began last May after allegations against present and former members of Cleveland Police Authority (CPA).
Her Majesty's Inspector of Constabulary (HMIC) Roger Baker appointed Mr Bristow to lead a criminal inquiry into allegations surrounding insurance claims, hospitality, and the award of police contracts from 2006 to 2009.
Codenamed Operation Sacristy, it has been described as a long and complex inquiry.
Rebian Solicitors said today's action follows a period of 10 months in which there have been no further criminal interviews or allegations against Mr Price and Mr Bonnard.
The lawyers said Operation Sacristy's legal adviser Leonard Miller said "the issue on which the search warrant was granted is not now being treated as a criminal matter".
A spokesman said: "Mr Price had serious concerns about the lawfulness and professionalism of aspects of the North Yorkshire and the Warwickshire-led inquiries and he raised these concerns directly with both Mr Baker and Mr Bristow."
The solicitors said Mr Price was concerned that documents were seized unlawfully and by someone who was a potential suspect in the inquiry.
"As 'data controller' of Cleveland Police, Mr Price was asked to provide further documents which appeared to have no relevance to the inquiry," Rebian said.
"The provision of documents in these circumstances could have given rise to an offence under the Data Protection Act, thereby potentially exposing Mr Price to criminal proceedings."
Mr Price said: "It is now 10 months since my arrest and detention, my name and reputation has been dragged through the mud, it has badly affected my health and I remain on bail suspended from the job I love.
"I remain baffled as to why I have been subjected to this treatment but it would appear it is down to my refusal to act unlawfully.
"I have now also been informed that the matter on which the search warrant was issued is not now being treated as criminal.
"I am totally innocent and determined to clear my name. I also believe the public, who are funding the bill for this inquiry, deserve to know exactly what has gone on.
"This legal action is the first step in that process."
Mr Bonnard said: "I would describe what happened to me and my family as feeling like a plane crash in my life. The impact is heightened by the fact that I was born and raised in the local area.
"I have served policing for 25 years and working with an excellent workforce, Sean and I turned Cleveland Police into one of the best forces in the country.
"Now I am suspended and subject to what I believe is an unnecessary, disproportionate and highly expensive investigation that the public are funding."