Senior civil servants exaggerated the seriousness of the leaks from Government that prompted the Damian Green police probe, a committee of MPs has said.
The Home Affairs Committee said frustration at the string of leaks may have led officials to give Scotland Yard an "exaggerated impression" of the damage they were doing.
The MPs said there was a "clear mismatch" between the contents of the letter to the Metropolitan Police asking officers to investigate and the description of the leaks provided by Home Office Permanent Secretary Sir David Normington.
The letter said the Home Office leaks had caused "considerable damage to national security". The committee said this description was "unhelpful" and "hyperbolic" and raised the question of whether the police would still have investigated without it.
In his evidence to the committee, Sir David said the letter reflected concerns about leaks from across Government. But the letter, which was written by Cabinet Office director of security and intelligence Chris Wright, referred only to leaks from the Home Office, the Committee said.
In their report, Policing Processes of Home Office Leaks Inquiry, the MPs support the use of "disciplinary action" against officials who leak material.
They said civil servants in this case followed the correct procedure for investigating leaks.
But they said that in future the bar should be set higher for when police are called in and detectives notified only when there is an apparent breach of the Official Secrets Act.
Mr Green's arrest and the raid on his House of Commons office and home caused outrage in Westminster after it emerged police did not have a warrant to search the Parliamentary estate. But the report said officers, under the command of former Assistant Commissioner Bob Quick, did not need one because they first sought consent.
Mr Green, the Tory immigration spokesman, and Christopher Galley, a junior civil servant working at the Home Office, were arrested within days of each other in November last year under common law offences relating to misconduct in public office. Both will answer bail on Monday.
