OTTAWA - Documents show the Harper government called in the RCMP to investigate a politically embarrassing story involving the decision to sole-source the purchase of the F-35 stealth fighter, claiming it was a breach of national security.

The Mounties conducted a five-month review into an alleged leak of cabinet documents under the Security of Information Act, which was recently used to charge a naval intelligence officer in an apparent spy case.

Records obtained by The Canadian Press under the access-to-information law show investigators had doubts almost from the outset in July 2010 that any laws were broken by the Globe and Mail story.

The story revealed angst within government about possible alienation from Washington if a competition was held to replace the air force's CF-18s.

Still, the review pressed ahead and drew in one of the RCMP's four Integrated National Security Enforcement Teams, whose job it is to chase terrorism threats.

The probe was shut down in December 2010 for lack of evidence.