The prime minister has rejected David Cameron's allegation that ministers act like "giant franking machines", signing letters without taking responsibility for the problems within their departments.
After a week in which the Home Office has been hit by a series of rows, the Conservative leader asked why junior department minister Joan Ryan is "still in her job".
He told the Commons that she had said she "knew nothing" about the latest records fiasco involving the recording of details of crimes committed overseas.
But, added Cameron, the minister had been signing and receiving letters on the issue since October.
Tony Blair said the backlog "was not drawn to her attention" by officials. "There is an internal inquiry in place," he added.
And there were "no significant public protection issues" that had arisen so far in relation to Criminal Records Bureau checks.
But Cameron said: "The prime minister's defence seems to be that the minister knew about the problem but not about the backlog - but the problem was the backlog."
He said ministers should "show some judgement rather than just operate like giant franking machines signing letters".
And the Tory chief said the text of the letters between the Home Office and the Association of Chief Police Officers, which is responsible for managing the records, should be published.
The comments prompted the prime minister to defend his junior minister.
"It simply is not correct to say that the problem was the backlog alone," he said.
"The problem was that there was no proper system and hadn't ever been a proper system for the exchange of information between European countries."
Blair also said it was a problem that "every country" had experienced. "Prior to 1999 there were absolutely no records kept at all," he told MPs.
And he rejected calls to publish the letters immediately.
"There is an inquiry underway and when the inquiry completes its investigation, everything will be published fully so that people can see it."
In response to further questions, the prime minister also said that the inquiry would look at the role played by ministers.
"Of course it will look at the role played by ministers, it will look at the role played by everybody," he told the Commons.
Cameron said it was wrong to ask the head of personnel at the Home Office to investigate the row.
And he linked the row to other Home Office problems involving failings with open prisons, immigration and control orders.
"The government's response to things that go wrong is to put junior officials in charge of an inquiry.
"Doesn't it show that this government and these ministers are interested in protecting themselves and not in protecting the public."
