Bob Quick said the First Secretary of State’s claim that he is a “tainted and untrustworthy source” is “deeply unpleasant” and “hurtful”, and insisted everything he has alleged is accurate and in good faith.
He claimed “a vast amount of pornography” was found on Mr Green’s computer in the notorious 2008 raid on his Commons office and that logs showed it had been viewed “prolifically” and in working hours.
Mr Quick, who has been condemned by Met chief Cressida Dick, the police watchdog and other senior officers for leaking the porn allegations, confirmed that he is threatening to sue Mr Green.
He has called on the Cabinet minister to retract his allegations against him, saying he is not motivated politically and bears no malice to him.
In a defiant eight-paragraph statement, Mr Quick said: “Damian Green called me a liar in the statement he tweeted on 4 November 2017. That is completely untrue.
“Everything I have said is accurate, in good faith, and in the firm belief that I have acted in the public interest.”
Mr Quick defended the raid on Mr Green’s Commons office, which he ordered when the Labour home secretary at the time, Jacqui Smith, demanded a police investigation into leaks to Mr Green, then a shadow Home Office minister.
He said: “During an investigation of his parliamentary office in 2008, it was reported to me and to other senior officers that a vast amount of pornography was discovered on the computer in Damian Green’s parliamentary office, on his account.
“I was told that internet history data logs indicated that the material had been viewed prolifically and in working hours.”
And in an apparent attack on the Commons authorities, Mr Quick said: “I recommended that the issue be referred to the Parliamentary Commissioner for Standards. As far as I know, no such reference was made.
“In view of this and the present Cabinet Office investigation into Damian Green, I contacted Sue Gray (the Cabinet Office’s head of ethics and propriety) in early November 2017.”
Mr Quick also gave his account of how the computer porn allegations against Mr Green now being probed by Ms Gray came into the public domain.
“Shortly afterwards, a journalist from the Sunday Times contacted me to say that he had obtained a draft statement prepared by me some years ago for the Leveson Inquiry,” he said.
“I did not approach the Sunday Times with this information.”
Mr Quick defended Neil Lewis, a retired Scotland yard detective who worked for him, after he claimed he found thousands of thumbnail pornographic images on computers seized in the 2008 raid on Mr Green’s office.
“Following Mr Green’s deeply unpleasant and personal attack upon me, I was contacted by Neil Lewis, who had undertaken the interrogation of Mr Green’s hard drive in 2008,” Mr Quick said.
“Mr Lewis offered me his support, and I believe him to be a man of integrity, similarly acting in the public interest. I reported Mr Lewis’ contact and the evidence he was able to provide to Sue Gray on 6 November 2017.”
Mr Quick added: “I wish to make it clear for the avoidance of any doubt or further speculation that I am in no way motivated politically and bear no malice whatsoever to Damian Green.
“This is despite unfortunate and deeply hurtful attempts to discredit me. Everything I have said about this matter has been in good faith, and in the firm belief that I have acted in the public interest.
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“I invite Damian Green publicly to retract his allegations against me. I am considering legal action.”
A spokesman for Mr Green said: “It would be inappropriate for Mr Green to comment while the Cabinet Office inquiry is ongoing and while the Metropolitan Police is investigating the conduct of former officers.”