A former Scotland Yard chief was aware pornography had allegedly been found on Damian Green's office computer during a 2008-9 police probe, he has said.
Sir Paul Stephenson, the Metropolitan Police Commissioner between 2009-11, said he was briefed about the claims but regarded them as a "side issue".
The allegations were first made public last week by former Met Assistant Commissioner, Bob Quick.
First Secretary of State Mr Green said his accusers had "ulterior motives".
Mr Green, who is Prime Minister Theresa May's second-in-command, said: "I reiterate that no allegations about the presence of improper material on my parliamentary computers have ever been put to me or to the parliamentary authorities by the police.
"I can only assume that they are being made now, nine years later, for ulterior motives."
But Mr Quick, who led the investigation into Home Office leaks which saw Mr Green's Commons office being searched, says pornography was found on a computer there.
Both Sir Paul and Mr Quick gave evidence to a Cabinet Office inquiry into Mr Green's conduct last week, led by senior Cabinet Office official Sue Gray.
The inquiry, which is being held behind closed doors, is also looking at a separate claim that Mr Green, made inappropriate advances towards a female Conservative activist in 2015. He also denies that allegation.
Speaking to the BBC, Sir Paul said he thought the claim about Mr Green "wasn't relevant to the criminal inquiry" into Home Office leaks, which began in October 2008.
Mr Green's home and office were searched as part of that probe and he was briefly arrested in November that year, but the then shadow immigration minister faced no further action.
A review of the police inquiry found that "less intrusive methods" could have been used.
Referring to the pornography allegations, Sir Paul said: "I regret it's in the public domain.
"There was no criminality involved, there were no victims, there was no vulnerability and it was not a matter of extraordinary public interest."
Sir Paul added that it was not Scotland Yard's role to "police the workplace".
The Met declined to say whether it was helping the Cabinet Office investigate the claims, but said in a statement: "As this is not our inquiry the MPS does not believe it is appropriate to comment upon it."