Justin Bieber strips on live TV

Justin Bieber stripped down to his underpants on stage last night (09.09.14) after receiving boos from an unimpressed crowd.

The 20-year-old singer was making a surprise appearance at charity fundraiser event Fashion Rocks in New York when he decided to ditch his clothes in order to show off his muscled physique.

The 'As Long As You Love Me' hitmaker and model Lara Stone, 30, were introducing a performance by Rita Ora which featured Calvin Klein jeans and underwear, prompting Justin to show off his own.

Walking on stage to loud boos, Justin asked: "So, uh, I actually don't feel comfortable unless I'm in my Calvin's so ... is that cool?"

The rebellious youngster was encouraged by Lara to take his gear off, despite the audience objection, and proceeded to shed his entire outfit apart from his Calvin Klein underwear. 

He then tried to encourage the crowd to stop booing and to start cheering.

After the event, Justin joked on Twitter: "Grandma always said kill 'em with kindness...and then strip on live national tv. Lol (sic)"

The troubled pop star has had multiple run-ins with the law this year including charges of assault and dangerous driving, but it was recently reported he is seeking help from a therapist.

BANG! Showbiz