The Metropolitan Police will not investigate the leak of MPs' expenses to a newspaper, Scotland Yard has said.
Senior officers and Crown Prosecution Service solicitors decided that a police inquiry would not be in the public interest.
Commons authorities had called in the Met after the Daily Telegraph published details of MPs' expenses claims.
Met Commissioner Sir Paul Stephenson said the force was working with the CPS to study whether MPs broke the law.
The decision not to investigate the leak was taken at a meeting between the CPS and officers from the Met's Economic and Specialist Crime Command, a Scotland Yard spokesman said.
He added that they concluded that a public interest defence would be a "significant hurdle" to any successful prosecution.