Celeb SAS: Who Dares Wins Chief Instructor Rudy Reyes has reignited his feud with the series' former frontman, Ant Middleton.
American SEAL Rudy, 50, has slammed the Brit he replaced, calling him "immature and narcissistic".
He also bragged he could beat adventurer Ant, 42, in a brawl.
Speaking on the Anything Goes podcast, Rudy - who has labelled Ant 'misogynistic' in the past - was asked by presenter James English how he feels about Ant "taking shots" at him.
"He's very immature, he's a very immature person," Rudy responded.
The hunky star of the C4 hit continued: "It's obvious how narcissistic he is. And of course, you know what, if he was ever face to face with me he wouldn't say a thing. He'd have no chance against me."
Rudy laughed and then added: "Believe that," which he then repeated for emphasis.
"I've always wished him the best," Rudy then said. "But I believe he has painted himself into a corner. He runs his mouth all the time and he treats people poorly. That's all I have to say."
It comes as former chief Ant took to Twitter with a furious rant, hitting out at Rudy in a string of messages and reposts from fans.
The reality TV star, who was fired from SAS: Who Dares wins after a series of high profile gaffes, which included a tweet about the Black Lives Matter movement - was clearly unhappy with his replacement.
Most read in Reality
"If a US Marine tried to run a Delta Force selection process, he would be laughed at and get a good old fashion kick in," he penned.
A fan replied: "They tried to make the other guy to look like you with a wig on," to which Ant brutally replied: "And uglier."
"What people don’t realise is that it comes under ‘comedy’ now where before it was factual entertainment," he continued.
"When you take the heart out of the show, it dies. RIP indeed."
He went on to repost a snap of Rudy shared by a fan, with the caption: "When you order Ant Middleton from Wish."
"This one always makes me chuckle, so true," he concluded his rant.
The former active duty United States Marine has replaced Ant on SAS Who Dares Wins as well as the celebrity version.