The 82-year-old entertainer is believed to have made the comments during filming of the Strictly Come Dancing Christmas special on Monday, where he regaled the studio audience with his thoughts on Walsh's previous comments that he "shouldn't even be alive".
According to The Mail On Sunday, Forsyth declared: "Louis Walsh said I should be dead. He said in print that I should be dead by now. Can you believe that from a jumped-up karaoke judge?"
The Price Is Right host proceeded to mock Walsh's fellow judge Simon Cowell, as well as The X Factor itself, by branding the show as style over substance.
"It looks like a fireworks display with singers. It’s not my kind of thing. If I was still doing Play Your Cards Right I would love to have done the question, 'We asked 100 people if Simon Cowell turned up with lovebites all over his body would, they be self-inflicted? 99 people answered yes and the odd one out was Dale Winton - but only because he didn't understand the question'."
Walsh reportedly responded to Forsyth's remarks by saying: "Bruce should just retire. His comments are the sign of old age. He’s too old to be on TV. He should just bow out gracefully now at the top of his game and go home to sit on his sofa and drink Horlicks."
The rivalry between the pair started after they attacked each other's shows, with Walsh claiming that Strictly was "finished" and Forsyth branding The X Factor as "embarrassing".