ITV News revealed in August that Mr de Menezes, who was killed after being mistaken for a terrorist, was being held down when shot by firearms officers after it was passed documents from the Independent Police Complaints Commission's investigation into the shooting.

Copies of documents are believed to have been obtained by the journalist, who is a news producer.

The story was hailed as one of the biggest scoops in the history of British television news and ITV has entered it for the Royal Television Society awards.

The leak from the IPCC's investigation included witness statements and photographs that undermined early accounts by the Metropolitan police of why Mr de Menezes was shot in a train carriage at Stockwell tube station on July 22 last year. The leak is being investigated by Leicestershire police who arrested the journalist in October and raided his home.

An ITV News insider said police seemed to be looking for evidence that money was paid for the statements. The source said no money was paid as ITV News did not have large sums of money available to offer for scoops, and if the IPCC source who leaked the documents had been motivated by money then they would have gone to a tabloid newspaper.

A 43-year-old IPCC employee was also arrested and has now resigned from the commission. Leicestershire police said that a 30-year-old woman was also arrested on suspicion of conspiracy to steal. All three people who have been arrested remain on police bail.

David Mannion, ITV News's editor in chief, told the Guardian: "We absolutely stand by the story, the way we covered it and the way we got the story; it was to our usual high editorial standards."