The policeman who led the investigation into the role of Damian Green in the leaking of documents claims that vital details about the inquiry are being covered up.

Bob Quick, former assistant commissioner of the Metropolitan Police, said of two reports that have criticised the inquiry and the arrest of the Shadow Immigration Minister: “I am disappointed that all publishable facts relevant to this case have not been disclosed. The public are entitled to all the facts in this case, given the scale of the controversy and in order to appreciate why prosecutors supported a continued investigation.”

Mr Quick, who left the Met before the Green inquiry was completed, did not specify what documents he wanted it to publish. It is understood, however, that detectives uncovered significant material when they won a legal battle over parliamentary privilege and were allowed to examine computers and documents seized from the Conservative MP’s office.

Mr Green’s arrest and the search of his Commons office sparked a political row and criticism of the Met. There was concern over the politicisation of policing after Boris Johnson, the new Conservative Mayor of London, ousted Sir Ian Blair as commissioner. But Mr Quick told The Times that he had been obliged to look into the MP’s relationship with a civil servant, Christopher Galley, who admitted that he leaked documents. “We had a serial leaker in the private office of Jacqui Smith, the Home Secretary. She was in charge of national security,” he said. “It would have been indefensible not to investigate what this man has leaked and to whom.”

Mr Quick spoke out after two reports criticised his inquiry. One, by Denis O’Connor, Chief Inspector of Constabulary, said that the police should investigate only the most serious Whitehall leaks, involving national security or serious criminality, and leave issues of political embarrassment to departmental security. Mr O’Connor said that the police, Parliament and Whitehall should agree a framework for inquiries over political matters covering when information was protected by parliamentary privilege.

A second report, by Sir Ian Johnston, then Chief Constable of British Transport Police, strongly criticised the manner of Mr Green’s arrest in his Ashford constituency by anti-terrorist officers. It said: “On balance I think the operational aims could have been achieved by the use of less intrusive methods. My view is that police actions were disproportionate.”

Mr Quick said that the Johnston review was a disputed document. The report has been secret for ten months and was published only after passages were redacted when concerned parties highlighted omissions and inaccuracies.

Mr O’Connor’s report revealed that serving senior Met officers had joined Mr Quick in taking issue with the finding of the Johnston review that Mr Green’s arrest was disproportionate. It said: “Senior ... officers responsible for making the decision sanctioning his arrest did not and do not agree with this conclusion and contend it was proportionate.”

Speaking at the publication of his report, Mr O’Connor said that the leak investigation coincided with a charged atmosphere. He said: “The commissioner was standing down, there was a super-heated environment where they [officers] were concerned about any decision they made being misinterpreted. They wanted to avoid at all costs appearing to be partial ... but good intentions are not enough when the stakes are so high.”

Mr O’Connor criticised the Cabinet Office letter to the Met that sparked the inquiry. He called for Whitehall to improve security and vetting and urged departments to be more cautious about involving the police in political matters. “The smooth running of government is not an obvious matter for the police,” he said. “The police are generally considered to be part of the State but they are not an instrument of the executive as such.”

Assistant Commissioner John Yates said: “We accept that some elements of the inquiry could have been carried out differently, and lessons learnt from this have already been factored into how we conduct this type of inquiry.”

No charges were brought against Mr Green or Mr Galley. The civil servant was dismissed for gross misconduct.

Exchanges between civil servant and MP

In an e-mail in August 2008 Mr Galley asked Mr Green if he wanted to meet. He replied: “Anywhere we won’t see your colleagues! Do you know the Balls Brothers? ... I will be in the back bar, which is usually quieter.”

In 2007 he wrote: “Thank you for your recent communications. As ever these have been extremely useful and I hope that you can keep them up in your new post.” It was one of five notes on Commons notepaper.

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