Phil Mickelson has denied placing bets on the outcome of the 2012 Ryder Cup made by a former gambling associate in a forthcoming memoir.

In a statement distributed to US media, Mickelson hit back at claims by professional US gambler Billy Walters, who said the six-time major winner tried to place a $400,000 bet on the 2012 Ryder Cup in which he was playing.

Walters' revelations were made in an excerpt of his memoir "Gamble: Secrets from a Life at Risk" published by the FirePit Collective website on Thursday.

Walters, a former close associate of Mickelson before their relationship soured when Walters was accused of insider trading, also claimed the golfer has placed bets worth more than $1 billion during his career.

In his statement, however, Mickelson strongly denied betting on the Ryder Cup 11 years ago, when Europe made an astonishing final-day fightback to win what has become known as the "Miracle of Medinah."

"I never bet on the Ryder Cup," Mickelson said in the statement. "While it is well known that I always enjoy a friendly wager on the course, I would never undermine the integrity of the game."

Walters claimed he rebuffed Mickelson when the golfer asked him to place $400,000 on the US team to win the Ryder Cup.

Mickelson, who has previously spoken about his struggles with gambling, once again reiterated that he has worked to tackle the problem through therapy.

"I have also been very open about my gambling addiction," Mickelson said. 

"I have previously conveyed my remorse, took responsibility, have gotten help, have been fully committed to therapy that has positively impacted me and I feel good about where I am now."

Mickelson triggered uproar in world golf last year after becoming one of the earliest and highest-profile defectors to the Saudi Arabia-backed LIV Golf circuit in a lucrative deal reportedly worth $200 million.

rcw/sev