London: Home Secretary Jacqui Smith is due to make a statement on the arrest of Damian Green after the Commons Speaker said police who searched the Conservative MP's Westminster offices did not have a warrant.

Michael Martin said police had failed to inform the parliamentary official who agreed to the search, of her right to insist on a warrant from a judge first.

Legal experts said, if correct, this would mean the police search was unlawful.

The acting head of Scotland Yard has said the investigation was "thorough and lawful". Martin did not say whether he or the official, Sergeant-at-Arms Jill Pay, had sought legal advice ahead of agreeing to the police raid.

Media reports said Smith would deliver the statement to the Commons on Thursday but a Home Office spokesman said a date had yet to be set.

Ignorance

Smith, who is responsible for policing, has insisted she knew nothing about the impending action against Green until detectives had swooped.

Many MPs are furious that the Speaker failed to uphold ancient parliament privileges by letting the police search the office of the Tory immigration spokesman last week. Martin said on Wednesday he had not personally authorised the search.

He told MPs he was informed by the Sergeant-at-Arms early last Thursday that an MP's office might be searched, but he was not told that the police lacked a warrant.

Paul Stephenson, Acting Commissioner of the Metropolitan Police, said officers had received written permission for the raid from the Sergeant-at-Arms.

But Martin said the police had not explained to her that she was not obliged to consent or could have insisted on a warrant.

No proper orders

Scotland Yard had no search warrant to raid MP Damian Green's office.

Leading QC Geoffrey Robertson said the raid was therefore unlawful. He said: "It was an unlawful search and Green should be able to obtain substantial damages for this."

Detectives who searched through files and removed computer equipment relied on a letter from a senior Commons official for authority to carry out the raid.