The Metropolitan Police will investigate The Times over allegations of email hacking.
Labour MP Tom Watson asked for investigations into email hacking at the News International paper after evidence at the Leveson inquiry into press ethics about the conduct of a Times reporter.
Times editor James Harding told the inquiry that its reporter Patrick Foster had been issued with a formal warning for professional misconduct after gaining unauthorised access to Lancashire detective Richard Horton's email account.
The paper named Horton as the author of the Nightjack blog in 2009.
"When [Foster] informed his managers that, in the course of his investigation he had on his own initiative sought unauthorised access to an email account, he was told that if he wanted to pursue the story he must use legitimate means to do so," Harding wrote in a letter to the inquiry.
The high court ruled against granting Horton anonymity as the author of the blog detailing his career as a detective after The Times was able to prove that it had gained sufficient legitimate proof of his identity for a story to be run.
Foster denied that legitimate proof had been found. He told police that it was "clear that a crime had been committed" while it was "almost certain that the judge had been misled" into believing that The Times had gained knowledge of Horton's identity through entirely legitimate means.
"Officers from Operation Tuleta [the investigation into computer hacking ] are in contact with Mr Watson in relation to specific issues he wishes to raise and we are not prepared to give a running commentary on the investigation," said a Met spokesman.