The home secretary said the case was far from routine
Jacqui Smith has promised to look again at how the Home Office handled issues relating to the arrest of Conservative MP Damian Green in a leak inquiry.
The home secretary told MPs that, given its sensitivities, some matters relating to the case would be reviewed.
This would not happen until the police concludes its investigation and while further criminal action is possible.
Ms Smith reiterated that she was not told of Mr Green's arrest in advance, a fact a Tory MP said was "astonishing".
The police's decision to detain the shadow immigration minister for nine hours in connection with a Home Office leak inquiry and search his Westminster office angered MPs.
Appearing before the Home Affairs Select Committee, Ms Smith and the top civil servant at the Home Office - Sir David Normington - were asked to make clear when they knew of the police operation and Mr Green's arrest.
Sir David said he was called by Bob Quick, the Met officer leading the investigation, at about 1.45pm on 27 November to tell him that officers were to search the office of a frontbench Tory.
Sir David asked who the MP was and said he was "extremely surprised" by the news.
He then replied: "Well, I hope you have the evidence for that."
The home secretary, who was in meetings in Brussels, said she was told of the news at about 2.20pm.
Sir David said he was then informed of Mr Green's arrest at about 2.25pm and decided, at once, to inform the home secretary and the prime minister.
Ms Smith said she learnt of this development at about 3.00pm.
Opposition parties have continued to question Ms Smith's version of events surrounding Mr Green's arrest.
Tory MP David Davies said many people would find it "astonishing" that she did not know of this in advance.
Ms Smith said she was told about a small number of high-profile arrests in advance, normally in counter-terrorism cases.
But referring to the recent cash for honours investigation, she added: "There is a precedent for not informing the home secretary about politically sensitive arrests."
Ms Smith said she would not comment on the police investigation but acknowledged that the case was not "routine" and there would be a review of how the Home Office handled key matters to see if lessons could be learnt.
Mr Green has denied any wrongdoing, saying he released information given to him in the public interest. He has not been charged with any offence.
Defending the Home Office's decision to call in the police, Ms Smith said this was justified because there had been a series of "systematic" leaks undermining the department.
As the identity of the leaker was unknown as that stage and given the nature of the information held by the department, it was clear sensitive material could be vulnerable, she added.
Asked about the seriousness of the leaks, Sir David said he knew of "at least" one piece of leaked information in the past two years which had implications for national security.
But he acknowledged "most" of the information reported to have been leaked in recent times did not relate to matters of national security.