Home secretary Jacqui Smith has made a statement to the Commons explaining her role in the Green affair.
She reiterated her lack of knowledge of the arrest, but launched into a robust defence of the police investigation - which she said was initiated by a phone call from the Cabinet Office.
Describing the leaks which triggered the investigation as a "systematic leaking of confidential information over a sustained period," Ms Smith insinuated the issue had an impact on national security.
Shadow home secretary Dominic Grieve replied: "The issues at stake are indeed very serious."
He described the arrest as "heavy handed and incompetent at best and at worst an assault on our democracy."
Pointing his finger at the home secretary, Mr Grieve continued: "Who is in charge of the police if she isn't?"
Ms Smith also faced angry reponses from the Liberal Democrat benches, with home affairs spokesman Chris Huhne asking her if she feared an actual leak affecting national security or a potential breach.
"Does she agree the muddle she has landed herself in should be clarified?" Mr Huhne argued.
He also called for legal protections for whistleblowers.
Ms Smith also faced criticism from her own benches with former home secretary John Reid suggesting he would not have been as placid about the arrest if he had been home secretary.
"Sometimes it behoves home secretaries to deal with issues calmly, as in this case," Ms Smith replied.
It has also been revealed that various other police investigations into government leaks are currently ongoing.
Earlier, the Conservatives turned their fire on Harriet Harman, the leader of the House, after the motion on the Green arrest issued today differed to the Speaker's statement yesterday.
Theresa May, Ms Harman's opposite number, said the motion immediately adjourned the committee speaker Michael Martin established yesterday until criminal proceedings are finished - potentially months from now.
She also raised serious concerns that police may have been able to access all MPs' emails and files when they accessed Mr Green's computer.
Ms Harman refused to be drawn on that, saying: "I am not going to respond to her invitation to comment on the police investigation.
"As far as security of honourable members' details is concerned, a security matter is a matter for the House authorities."
Ms May said: "It's the leaders job to represent the House. This motion manifestly fails to do so."
Last night, leader of the House Harriet Harman repeatedly refused to back Mr Martin, saying: "I am not saying I've got full confidence in anything or anybody I'm just telling you what the facts are".
Appearing on Newsnight, the former lawyer was then asked if Mr Martin had her confidence several times but she consistently refused to answer.
Housing minister Margaret Beckett stood up for Ms Harman on the Today programme this morning.
"I think what was unfortunate about yesterday is that there's a lot of people looking around for someone to blame," she said.
"It didn't sounds to me like this was all the speaker's fault, and I don't blame Harriet for not wanting to be put in that situation".
But the prime minister stood up for Mr Martin today, saying he had a "great deal of confidence" in him.
Conservative backbencher Richard Bacon is leading a campaign for a new speaker.
The public accounts committee member described Mr Martin's performance when giving his statement to the House yesterday as "lamentable and shocking".
"I no longer believe the speaker can stay in his job," he wrote on his website.
"I have no confidence in the speaker's willingness or ability to defend parliament or me as an MP so that I can defend the interests of my constituents. He has to go. It is that simple."
Mr Martin made an unprecedented statement to the House yesterday, in which he seemed to pass the blame onto Jill Pay, the serjeant at arms, for allowing counter-terrorism officers to search Damian Green's parliamentary office without a warrant.
He has established a committee of senior members to look at the affair and for its conclusions to be debated in the Commons.
According to Mr Martin's account, he was not told there was no warrant, although there was an implicit assumption he did not ask Ms Pay if there was one.
There was also criticism of the police for not informing Ms Pay she was under no obligation to allow them entry.
"I was not told that the police did not have a warrant. I have been told that the police did not explain, as they are required to do, that the serjeant was not obliged to consent or that a warrant could have been insisted upon," the speaker said.
"I regret that a consent form was then signed by the serjeant at arms without consulting the clerk of the House. I must make it clear to the House that I wasn't asked the question of whether consent should be given or whether a warrant should have been insisted on."
There were gasps in the House as Mr Martin gave his account and shouts of "shame".
But today assistant commissioner Bob Quick insisted the serjeant at arms had been fully briefed.
"The officers explained the nature of the investigation and the purpose of the search and were satisfied that the Serjeant at Arms understood that police had no power to search in the absence of a warrant and therefore could only do so with her written consent or that of the Speaker," he wrote.
"Prior to giving written legal consent, the Serjeant at Arms told the officers that she would seek legal advice."
Business secretary Lord Mandelson tried to turn fire on the Conservatives this morning, by suggesting the party was using the controversy as a smokescreen.
"I also have to say I think that for many Conservatives, it is a self-serving smokescreen, behind which to hide their own apparent collusion with a Home Office official who was allegedly systematically leaking Home Office papers to the Conservative Party, in order to pursue his own personal political ambition," he told Sky News.
"I would like to know from the Conservatives whether their frontbench and their leader knowingly colluded with that civil servant in riding a coach and horses not only through the Civil Service code but also through the law."
Mr Green's offices were searched last week as part of an investigation into Home Office leaks.
He was arrested and questioned for nine hours.