It started when things got rather heated between Louis and a reporter at a press conference in London last night.
Louis was at Wembley with his group 5 After Midnight answering questions about the final.
Asked what he'd do if Cheryl came back to the show, Louis responded: "Well Simon wouldn't invite Cheryl back because we have Nicole. We have Nicole and Sharon, we don't need another girl.
"So go and f**k off now! No silly questions, seriously."
He added: "It's not about Cheryl. Don't be stupid, man."
Although Louis' comments were more about the reporter and their "silly questions" than Cheryl, Liam seems to have taken great offence to the mere mention of his girl.
Which originally came from the reporter, rather than Louis.
"Congratulations Louis Walsh for setting the worst example on handling media for his band who are about to step into a very hard industry," Liam, who is dating Cheryl, wrote on Twitter this evening.
He added: "Maybe it's about time you realise it's not all about you and shut the f**k up for once, let them speak"
Cheryl, who quit The X Factor as a judge earlier this year, then cryptically tweeted: "Oh.. 🐸☕️🌚"
This weekend sees The X Factor 2016 final where Louis' group 5 After Midnight, Sharon Osbourne's act Saara Aalto and Nicole Scherzinger's boy Matt terry will go head to head.
The live shows begin Saturday at 8PM from Wembley Arena.