Police mole hunts have begun into other Whitehall leaks in addition to the Damian Green investigation, the Home Office disclosed yesterday as in-fighting intensified between Scotland Yard and the Commons authorities over the raid on the Tory MP's office.
Jacqui Smith, who was forced to make an emergency statement to MPs on the affair, suffered the embarrassment of hearing her predecessor as Home Secretary criticising her handling of Mr Green's arrest.
With ministers refusing to express confidence in Michael Martin's performance as Speaker in the wake of the raid, suggestions are growing that he will step down at the next election.
The Government has long believed that Christopher Galley, the Home Office official arrested for passing a series of documents to Mr Green, is not the only mole in Whitehall. Repeated leaks of tax plans, such as details of last month's pre-Budget report, have raised suspicions that an official in the Treasury or in HM Revenue and Customs could be sending private papers to the Opposition.
Asked in the Commons about the suspected Treasury leaks, Ms Smith replied: "There have been other situations where the police have been invited to investigate by the Cabinet Office."
The parties clashed over the nine-hour detention of Mr Green and the search of his two homes and Commons office. Ms Smith insisted she had not known in advance about the action against the shadow Immigration minister. Her predecessor, John Reid, told her: "I am surprised, to say the least, that you were not informed that your opposite number, effectively, was about to be arrested. If I had been told after the event that that had been done, I cannot think that I would have remained as placid as you have." She replied: "I think sometimes it behoves home secretaries to deal calmly with issues that are of significance."
Mr Green challenged her after she reiterated a police statement that he was held "on suspicion of conspiring to commit misconduct in a public office and aiding and abetting, counselling or procuring misconduct in a public office". Brandishing a copy of his arrest warrant, he said the words "counselling and procuring" did not appear on it. The police refused to comment.
The Met hit back yesterday at Mr Martin's claim that the raid was unlawful and that its officers did not explain to Jill Pay, the Serjeant at Arms, that they had no powers to raid Mr Green's office without the consent of the House authorities. Assistant Commissioner Robert Quick, who is leading the Home Office inquiry, said his officers fully explained the legal situation to Ms Pay, who gave written permission for the raid without a warrant.
The disparity between the two accounts will add to the pressure on Mr Martin, who granted an emergency three-hour debate on the Green affair on Monday. Two Conservative MPs have called for Mr Martin to quit.