That's according to fellow Australian golfer Cam Percy, who claims both men have already signed with the controversial Saudi-led breakaway league.
LIV Golf is bankrolled by Saudi Arabia's Public Investment Fund and has spared no expense in luring some of the biggest golfers in the world to play in the series.
The likes of Phil Mickelson, Dustin Johnson, Bryson DeChambeau, Henrik Stenson, Lee Westwood and Ian Poulter have all jumped ship, and now one of the most in-form golfers on the planet appears to have followed suit.
Smith won the 2022 Open Championship at St Andrews last month after also bagging the Players Championship earlier in the year and is currently the second-ranked golfer in the world, behind only Masters champion Scottie Scheffler.
Leishman, meanwhile, sits just outside the top 10 and is a former runner-up at The Open who has 13 professional wins to his name, including six on the PGA Tour.
"Unfortunate, yeah, they're gone," Percy told RSN radio.
"I had a long conversation with Adam Scott and he was very interesting talking to about it, just where it is.
"He said he met with these guys (LIV) in 2017 (and) they were ready do all this. So, the tour has known for a long time that this stuff's in the works.
"The more and more you look into it, some people don't care, some people have got a conscience and do care," he added.
"It really comes down to, you know, 'They just executed 80 people this week, just chopped their heads off'. They're not the nicest people in the world.
"Do you just look past that and go, 'oh well, I'm rich. I don't really care'. It's a tough one, it really is."
Smith sidestepped questions about LIV Golf when asked about it straight after his victory at The Open.
"I just won the British Open and you're asking about that? I think that's, pretty, not that good," he said.
"I don't know, mate. My team around me worries about all that stuff. I'm here to win golf tournaments."