Home Office 'not told of MP arrest'

Police informed officials only that they were intending to search the Tory immigration spokesman's Parliamentary offices, not that he was to be taken into custody, the sources said.

Delays in the message being received also meant senior civil servants were unaware of the raid until after it began.

The revelations reveal the extent to which the Home Office was kept in the dark over the investigation. The inquiry, which is led by Scotland Yard Assistant Commissioner Bob Quick, has already faced questions over the methods it used.

A review by British Transport Police chief constable Ian Johnston has raised concerns over whether the approach to the investigation followed best practice and policy guidelines. Mr Quick was forced to apologise and withdraw claims he made suggesting the Tories were seeking to undermine his inquiry.

The raid on Mr Green's private office, which was carried out without permission from the Speaker or a search warrant, provoked outrage from MPs and has led to a review of Parliamentary procedures.

It can also be revealed that the internal investigation carried out inside the Home Office found evidence implicating Christopher Galley, the junior civil servant who has admitted passing documents to Mr Green.

But the evidence emerged after Scotland Yard was called in. It was passed to officers and Mr Galley was arrested on November 19. Anti-terror police raided Mr Green's home and Parliamentary offices on November 27. He was arrested and held in custody for nine hours before being bailed.

The Crown Prosecution Service is expected to make a decision on whether or not to charge both Mr Green and Mr Galley in the coming weeks.

Home Secretary Jacqui Smith and Home Office Permanent Secretary Sir David Normington will face questions on the investigation at the Home Affairs Committee on Tuesday.