Mickelson had $40mn in gambling losses: biographer

US federal auditors probing Phil Mickelson's role in an insider trading case found he had gambling losses of more than $40 million from 2010 to 2014, according to an excerpt from Alan Shipnuck's forthcoming biography of the US golfer.

Shipnuck posted the excerpt from the unauthorized biography on the Firepit Collective website on Thursday.

The book, "Phil: The Rip-Roaring (and Unauthorized!) Biography of Golf's Most Colorful Superstar," is due to be released on May 17.

That's two days before the start of the PGA Championship, where Mickelson is the defending champion.

Mickelson became the oldest major winner in golf history when he won the PGA at Kiawah Island last year at the age of 50, but it's not yet known if he will defend the title at Southern Hills in Tulsa, Oklahoma.

Mickelson has not played since an uproar in February followed Shipnuck's publication of the player's explosive remarks concerning the Saudi-backed LIV golf tour spearheaded by Greg Norman.

The six-time major champion called the Saudi partners "scary," citing the 2018 murder of Washington Post journalist Jamal Khashoggi.

But he said he was willing to work with them if the breakaway tour provided "leverage" in efforts to force the US PGA Tour to alter policies that Mickelson said rob players of deserved money-making opportunities.

Mickelson was a relief defendant in a 2016 criminal insider trading case that sent gambler Billy Walters to prison.

Mickelson wasn't charged, but repaid almost $1 million made in the deal.

In the excerpt posted Thursday, Shipnuck, citing a source with direct access to the documents, writes that government auditors working the case investigated Mickelson's finances over four years from 2010 to 2014.

"In those prime earning years, Mickelson's income was estimated to be just north of $40 million a year," Shipnuck wrote. "That's an obscene amount of money, but once he paid his taxes (including the California tariffs he publicly railed against), he was left with, what, low-20s? Then he had to cover his plane and mansion(s), plus his agent, caddie, pilots, chef, personal trainer, swing coaches and sundry others.

"Throw in all the other expenses of a big life – like an actual T. Rex skull for a birthday present – and that leaves, what, $10 million? Per the government audit, that's roughly how much Mickelson averaged in annual gambling losses."

Mickelson's management company confirmed in April that he had sought a release from the US PGA Tour to play in the first event of the LIV tour, the LIV Golf Invitational near London June 9-11.

But in a statement Steve Loy, co-president of Sportfive management, stressed the player had not yet confirmed his participation