Justin Bieber's time-keeping improves for his second night at the O2 Arena

In case one of the two watches Justin Bieber has been wearing around London had stopped, a giant video clock ticked down the seconds till show-time on his second night at the O2 Arena. Unlike the previous night, when fuming parents and children complained he kept them waiting two hours, when the clock hit zero at 9pm, the singer promptly appeared.

Bieber said nothing on-stage about Monday's fiasco, and Tuesday's fans, perhaps reassured by the clock, seemed unconcerned. In the O2's corridors in the minutes before his arrival, young girls practised their screams, and a parent screamed for a pint at the bar. The massed roar when he appeared was in ear-splitting unison. After a bumpy 24 hours, the Bieber show seemed back on the road.

Earlier in the day, Bieber had apologised and promised to improve his time-keeping as angry parents demanded refunds after the singer's tardy appearance forced them to lead sobbing children to the exits.

Fans, who had paid up to £70 for tickets, had booed as they waited for the singer's arrival. Some concert-goers complained that they missed trains and were left stranded after Bieber finally hit the stage at 10.30pm. The 20,000 capacity venue was barely half-full by the time the over-running show drew to a close.

The US singer, who turned 19 on Saturday and has 35 million Twitter Beliebers, moved swiftly to quell what threatened to become a PR disaster.

He denied the claim that he had been two hours late but appeared to blame the media for inconveniencing him.

In a series of Tweets, he said: “Waking up to a crazy day. Last night I was scheduled after three opening acts to go on stage at 9.35 not 8.30, but because of some technical issues I got on at 10.10. So I was 40 minutes late to stage. There is no excuse for that and I apologise for anyone we upset.”

Bieber added: “My relationship with the media is not always easy but I'm trying” and said “since I have been here it hasn't been easy with the press at times.”

Bieber said: “However it was (a) great show and I'm proud of that…I'm all about the music and the performance and I respect my fans.”

But many Disbeliebers said they would not be coming back. John Lush, 48, an advertising manager, who took his 10-year-old daughter, said they were only able to stay for one song before they had to leave to catch the train home to Bromley, Kent.

He said: “I am absolutely livid. I don't think a refund would compensate the emotional damage he has done to my children. Giving money to a 10-year-old who couldn't see their hero is not enough, not when they have school the next day.”

Ellie Steadman, a blogger who said she worked at the O2 Arena, challenged Bieber's explanation. She wrote: “Bieber was due on at 8.30pm. Nobody had a clue what was going on, it had been hours since the support acts, the audience were past the point of patient, there was a LOT of booing. I found it stressful having to try to help parents and sobbing kids, people were leaving because of how late it was.”

Writing on her elliegracex blog, she said she was not aware of any technical difficulties delaying the star's arrival. She wrote: “Justin Bieber you are just a 19 year old whose world could be the complete opposite tomorrow if you don't start showing some respect and genuine care for your fans and people who work for and around you.”

In 2009, Madonna kept fans waiting an hour before performing at the O2 when she demanded that the air-conditioning was turned off inside the arena. Axl Rose of Guns N'Roses is notorious for keeping fans waiting until close to curfew time before hitting the stage.