Justin Bieber apologizes to outraged fans after they bash him for starting concert 2 hours late

Is Justin Bieber the biggest brat on the planet?

(And also by the way, what's up with those oversized hats?)

The 'Baby Baby Baby' singer acted just like one when he took hours to apologize to his young fans — and their outraged, overtired parents — after they accused him of taking the stage almost two hours late for a concert in London on Tuesday.

The singer made no mention of his tardiness on stage, but on Tuesday, in a tweet, insisted he had only been 40 minutes late, and blamed "technical issues."

After making his excuse, Bieber added: "There is no excuse for that and I apologize for anyone we upset. However it was great show and I'm proud of that."

Concertgoers said the teenage star appeared onstage at the 02 Arena on Monday at 10:30 p.m., when the start time had been listed as 8:30.

Bieber tweeted that he was scheduled to begin his performance at 9:35 p.m., after three opening acts. He claims he took the stage at 10:10 p.m.

But regardless of the exact time the Biebs actually started performing, many in the audience, who had been waiting for hours, faced the choice between leaving early or missing the last trains home.

"There were teenage girls crying outside," said financial analyst Louise Cooper, who had taken her 9-year-old daughter to the gig as a birthday present.

"The ladies sitting with us had to leave after 20 minutes and they had spent 70 quid (about $106) each on a ticket, which is really bad.

"It's one thing if your demographic is 50-year-olds, but his demographic is lots of little girls who need to go home and go to bed."

Tracy Wilson, who attended the show with her teenage daughter, said people began booing when Bieber had not appeared by 9:30. She called the lack of explanation "disgusting."

The venue apologized on its Twitter feed "to all the Justin Bieber fans for the lateness of his show tonight."

The post from the venue came immediately following the concert. Bieber's apology to his fans was not posted until well into the following day.

Critics said the Canadian star, who turned 19 on Friday, risked alienating fans by behaving with the same disregard for timekeeping as hard rock bands (Guns 'n Roses most infamously) often do

John Aizlewood in the Evening Standard newspaper said Bieber had shown contempt for young fans, leaving them "exhausted, disillusioned and probably late for school this morning."

Bieber, who is due to play three more nights at the venue Tuesday through Thursday, hasn't been having the best visit in the U.K.

Over the weekend, the pop star was highly criticized for tweeting he had the "worst birthday," after some members of his entourage were reportedly denied entry to a London club for being underage.

This after Bieber entered the club shirtless.

Bieber denied that he "brought underage people to a club" in a post on Instagram and claimed his birthday didn't go well "due to dummies pushing over my fans and being overly aggressive."

In a series of tweets about Monday night's concert, Bieber vaguely mentioned the controversy surrounding his London visit.

"Since I have been here it hasn't been easy with the press at times but I have loved it," Bieber tweeted.

"I never have any intent to upset or let anyone down. And I'm not okay with things being exaggerated. Once again sorry for anyone upset."

He promised that he would put on a "great show" Tuesday — and it would start on time.

The Associated Press contributed to this report.