[Photo:  Mickelson - EPA]

Remember last May’s blockbuster story that placed professional golfer Phil Mickelson 'smack dab' in the middle of an insider trading probe involving famed Las Vegas sports gambler, William 'Billy' Walters? Well, turns out that an FBI agent was the leak.

The unidentified FBI agent now admits he was a "significant source" for The Wall Street Journal and The New York Times, and prosecutors have referred the agent's leak to the U.S. Justice Department's Office of Inspector General and the FBI’s Office of Professional Responsibility.

Prosecutors claim they just learned about the incident - while preparing for a hearing on Wednesday on claims of government misconduct by lawyers representing Billy Walters. Defense attorneys also contend the probe was just now leaked to breathe life into it.

THE CASE.    Walters, who has built a fortune as a sports bettor, was arrested in May 2016 on charges that he traded on tips supplied by Thomas Davis, former chairman of Dean Foods, who has pleaded guilty and is cooperating with prosecutors. The case came 2 years after The WSJournal and The NYTimes published reports about the investigation citing anonymous sources.

The SEC in a related lawsuit said Mickelson, who has won 3 Masters pro golf titles, at one point bought Dean Foods' stock on a recommendation by Walters, to whom he owed money after placing bets with him. Mickelson was not accused of wrongdoing, but he reached an agreement with the SEC to pay back about $1 million the regulator said he earned trading shares of Dean Foods.