Singer was recording 'Alan Carr's Summer Specstacular' when 300 fans turned up.
Hundreds of young fans invaded ITV's London studios in an effort to meet Justin Bieber.
The 18-year-old 'Baby' singer was at the location to record 'Alan Carr's Summer Specstacular' when 300 girls stormed past security barriers.
The mob were fought back by only three security guards meaning they didn't stand a chance of defending the pop star.
A source told The Sun: ''It was genuinely scary. They're only teenage girls but they were hysterical and had just one thought on their minds -- to see Justin Bieber. It was pandemonium.''
Apparently television bosses managed to shut The Doors to the main building at the last minute.
Meanwhile, Justin is in trouble for punching someone in the groin.
Justin and his roadies play a game on tour where they have to protect their private parts to avoid being hurt.
But Justin accidentally delivered an unexpected punch to someone who wasn't part of the crew.
The 'Boyfriend' singer had a run in with a paparazzi photographer last Sunday (27.05.12), and the case is being referred to the Los Angeles County District Attorney for possible criminal prosecution.