Ashford MP Damian Green will not face any charges over allegations he leaked sensitive Home Office material.
The shadow immigration minister was arrested in November last year and his House of Commons office and constituency home raided by police in connection with the claims.
The MP always denied any wrong-doing and said he acted in the public interest.
In a statement issued today, the Crown Prosecution Service said it was not pursuing any charges.
The Director of Public Prosecutions, Keir Starmer QC, decided there should be no charges brought against MP Damian Green or Christopher Galley, following a Metropolitan Police Service investigation.
Mr Starmer said: "The evidence I have considered includes all the relevant documents seized by the police following searches of the homes of Mr Galley and Mr Green, and of Mr Green’s constituency and parliamentary offices, as well as other material including previous judgements and advice from counsel.
"I considered an alleged offence of misconduct in public office against Mr Galley and an alleged offence against Mr Green of aiding, abetting, counselling or procuring the alleged offence against Mr Galley, and of conspiring with Mr Galley for him to commit misconduct in public office."
The statement went on: "There is a high threshold before criminal proceedings can properly be brought for misconduct in public office. In considering whether the conduct of Mr Galley and Mr Green reached that threshold and in particular whether it represented such a serious departure from acceptable standards, and abuse of trust as to constitute a criminal offence, I have considered the extent to which there has been any actual damage arising, or the extent of any potential damage that could have arisen, as a result of their conduct. I have also had regard to the freedom of the press to publish information and ideas on matters of public interest.
"I have concluded that there is evidence upon which a jury might find that there was damage to the proper functioning of the Home Office. Such damage should not be underestimated. However, it has to be recognised that some damage to the proper functioning of public institutions is almost inevitable in every case where restricted or confidential information is leaked.
In a statement, Mr Green's lawyer, Michael Caplan, said: "Mr Green has always emphatically denied these allegations. The police need now to learn the lessons from their operations. There was no necessity to arrest Mr Green. He should have been asked to attend the police station voluntarily."
He added: "The search of his parliamentary office and the way it took place was highly questionable and no proper regard was given to issues of parliamentary privilege."