Corey Taylor and Machine Gun Kelly are locked in an ongoing feud.

The 'Rap Devil' star took aim at the Slipknot frontman, 47, during a festival performance at the weekend, where he mocked the heavy metal singer for wearing masks on stage and "talking s***".

The rock rapper had said on stage at Chicago's Riot Fest “You wanna know what I’m really happy that I’m not doing? Being 50 years old wearing a f****** weird mask on a f****** stage, talking s***.”

MGK - whose real name is Colson Baker - went on to claim their feud dates back to when he asked Corey to guest on a song for his album 'Tickets To My Downfall', which was released last year.

The 31-year-old star says he was annoyed by how "f****** terrible" the verse was and branded the 'Before I Forget' rocker "bitter".

He tweeted: “Corey did a verse for a song on tickets to my downfall album, it was f****** terrible, so i didn’t use it.

“He got mad about it, and talked s*** to a magazine about the same album he was almost on. yalls stories are all off. just admit he’s bitter. (sic)"

Corey then hit back when he took to Twitter to reveal his alleged communication with Travis Barker, who executive-produced the record for MGK, about the verse, in which the Blink-182 drummer alleged that the latter was happy with his contribution, but Corey ultimately decided it wasn't for him.

Alongside the screenshot, Corey wrote: "I don’t like people airing private s*** like a child. So this is all I’ll say: I didn’t do the track because I don’t like when people try to ‘write’ for me. I said NO to THEM. So without further ado…. #receipts

This is all I’m going to say about it."

In the email, Corey wrote: “Nothing personal, I just think if this is what MGK is looking for, someone else is the guy to do it. It’s ALL good, and I’m stoked for him - I hope you guys find the right fit for it. Hope you understand and I wish you guys the best with it.”

MGK was allegedly “super inspired” by Corey's vocals.

He told Corey via Travis: “Can u tell him he f*****' killed it and im stoked and HONORED he is even on it wtf !!! (sic)"

However, the Stone Sour frontman was not keen on the changes they had made to the song, which was called ‘Can’t Look Back’ and was a bonus track.

It read: “I sent Corey an idea for the second half of his verse and he can obviously say f*** it but it would be sick to see if it inspired anything or if he could try it like that.

“I laid a demo screami-ish type track under his first part of the verse that would be dope to hear in his ‘Psychosocial’ voice.”

MGK responded: “Basically, your verse was really bad. Respectfully, i was just telling you to rewrite it because it was really bad. respectfully. (sic)"

Over on his Instagram Stories, meanwhile, he wrote: “Hey, I got a question.

“What the f*** is y’all’s problem with me, man?

“I just chill, I make music, people talk s***… No-one’s hoing me, so I talk s*** back.”

Before MGK sparked the feud with the stage diss, Corey appeared to take a veiled swipe at the 'my ex's best friend' rocker for jumping from rap to punk rock on his latest LP.

Corey had said in an interview: “I hate all new rock for the most part. I [hate] the artists who failed in one genre and decided to go rock and I think he knows who he is.”

And MGK responded on the micro-blogging site: “Very odd that when an artist talks s***, and I respond, I’m the bad guy."