Dominic Grieve has condemned the claims as a "flagrant breach" of the detectives’ code of conduct and said their actions smacked of a "police state."
Retired Scotland Yard detective Neil Lewis had earlier claimed that "thousands" of thumbnail images of legal pornography had been found on Damian Green's parliamentary computer in 2008.
On Friday, he told reporters gathered outside his home that he will wait for the Cabinet Office to complete its inquiry before making any further comment on the allegations against him.
Separate claims that Green behaved inappropriately towards a female journalist, which he also denies, are also being looked at by the Cabinet Office.
Speaking on BBC Newsnight, Dominic Grieve, who served as Attorney General in David Cameron's government between 2010 and 2014, described the decision by the officers to release such information from a police investigation as "very worrying.".
"They choose to put material that an ordinary citizen would be prohibited from acquiring under data protection rules into the public domain on their own judgment," Grieve said.
"We give the police powers that other people do not have. They are not and must not be allowed to abuse those powers," he added.
Tory MP Jacob Rees-Mogg likewise attacked the "improper search" carried out in 2008 as well as Neil Lewis’s decision to comment now, insisting that Green has "nothing to apologize for or to answer for.".
"We have to rely on our police to be politically independent. They were acting in that instance as a tool of the then-government. This undermines the basis of democracy and evidence taken from an improper search, as a matter of justice, should not then be used,” he complained.
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Meanwhile, Brexit Secretary David Davis, who regards the police claims as “bogus,” has warned Prime Minister Theresa may not to sack Green, dismissing the claims as the result of a “wrongful attempt by former [police] officers to bring him down,” the BBC wrote.
