Rory McIlroy has been outspoken against Phil Mickelson and LIV Golf after the lefty joined the new league last year.

Despite the PGA and the Public Investment Fund, which financially supports LIV, coming to a merger deal and Mickelson's move to LIV now well over a year old, McIlroy is still taking jabs at the six-time major winner.

It was revealed earlier Thursday Mickelson allegedly has wagered over $1 billion on sports over the last 30 years.

A new memoir on Mickelson claims the 53-year-old asked his associate to place a $400,000 wager on the U.S. team to win the Ryder Cup in 2012. The U.S. lost in stunning fashion in what is now known as the "Miracle at Medinah."

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Phil Mickelson and Rory McIlroy at tee box

Rory McIlroy of Northern Ireland watches his shot from the sixth tee as Phil Mickelson of the United States looks on during the first round of the Zozo Championship @ Sherwood Oct. 22, 2020, in Thousand Oaks, Calif. (Harry How/Getty Images)

Mickelson participated in 12 Ryder Cups between 1995 and 2018. He did not make the team in 2021 despite winning that year's PGA Championship, becoming the oldest major winner ever at 51.

But McIlroy has an idea for Mickelson to stay involved in this year's competition that will be played in Italy next month.

"At least he can bet on the Ryder Cup this year, since he won't be a part of it," McIlroy said.

Billy Walters, author of the upcoming book "Gambler: Secrets from a Life at Risk," wrote that Mickelson called him about making a bet on the U.S. team for the Ryder Cup. Mickelson was on the squad with Tiger Woods and Bubba Watson and appeared to be confident about the team’s win.

Mickelson denied this claim later Thursday.

"I never bet on the Ryder Cup," he posted on X, formerly Twitter. "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 wrote that Mickelson’s gambling losses are estimated to be about $100 million. He says Mickelson in 2011 made 3,154 bets, about nine wagers per day. In a single day in June of that year, Walters claims, Mickelson made 43 bets on MLB games and took more than $143,000 in losses.

Phil and Rory at Ryder Cup

Phil Mickelson and Rickie Fowler of Team USA shake hands with Rory McIlroy and Andy Sullivan of Team Europe after their 1-up victory on the 18th hole green during the 2016 Ryder Cup at Hazeltine National Golf Club Sept. 30, 2016, in Chaska, Minn.  (Keyur Khamar/PGA Tour)

"It was nothing for Phil to bet $20,000 a game on long-shot, five-team NBA parlays," Walters, a noted gambler himself, added. "Or wager $100,000 or $200,000 a game on football, basketball, and baseball."

Citing his own "detailed" records and "additional records" from sources, Walters provided a look into Mickelson’s gambling habit between 2010 and 2014.

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Mickelson opened up to Sports Illustrated about his gambling in 2022 when asked about why he joined LIV after years on the PGA Tour.

"My gambling got to a point of being reckless and embarrassing," he said. "I had to address it. And I’ve been addressing it for a number of years. And for hundreds of hours of therapy. I feel good where I’m at there. My family and I are and have been financially secure for some time.

Mickelsen and McIlroy

Team USA's Phil Mickelson, right, and Team Europe's Rory McIlroy during the 41st Ryder Cup at Hazeltine National Golf Course in Chaska, Minn., Sept. 30, 2016. (Timothy A. Clary/AFP via Getty Images)

"Gambling has been part of my life ever since I can remember. But about a decade ago is when I would say it became reckless. It’s embarrassing. I don’t like that people know. The fact is I’ve been dealing with it for some time. Amy has been very supportive of it and with me and the process. We’re at a place after many years where I feel comfortable with where that is. It isn’t a threat to me or my financial security. It was just a number of poor decisions."

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McIlroy has been named a member for Team Europe for next month. It will be his seventh Ryder Cup after playing in each one since 2010.

Fox News' Ryan Gaydos contributed to this report.