A number of parents who were still furious about Bieber's lateness during Monday's gig at the O2 Arena reportedly intended to confront the teenage singer.
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However, they eventually left the hotel by the time Bieber got back there at 4.30am, reports The Sun.
Bieber is said to have thrown the V-sign at photographers and dropped his jeans to show his boxer shorts as he was driven back.
One fan's peeved father placed a banner outside Bieber's hotel with the phrase: "Justin Thiever".
The sheet also read: "You smoked my money and broke my daughters' hearts. Non Belieber."
> Justin Bieber: Has he lost the pop plot or are you still Beliebing?
Bieber did not arrive on stage until 10.20pm on Monday night (March 4), meaning many young fans had to leave early, while others had spent up to £331 a ticket.
It has been alleged that Bieber threw a tantrum at his family and entourage before the gig.
Watch Justin Bieber and Nicki Minaj's music video for 'Beauty and a Beat' below: