Former Skid Row frontman Sebastian Bach launched into a foul-mouthed tirade during a recent concert after allegedly spotting a fan bumping into his elderly mother in the crowd.

The rocker was performing in Toronto, Canada on 21 December (14), when he stopped the show to berate the audience member.

He said, "Hey, you wanna f**king stop the show? That's my f**king mother right there, you jack-off. I'm gonna f**king beat your f**king face in.

"Don't f**k around with my f**king mother if you f**king wanna get out of here alive. Don't anybody f**king touch my f**king mother or I'll jump right the f**k in here..."

Bach then asked his mum if she was Ok, before adding, "Any more idiots, man, and I'm f**king outta here. We're here to have a good f**king time, right? She's 70 f**king years old."

It is unclear whether Bach's mother was pushed or if someone was pushed into her.