It is the sad secret behind one of Australia's biggest rock bands. Craig Nicholls, lead singer of the Vines, is suffering from mental exhaustion and needs a break from touring, close friends say.

The news comes as police have launched an investigation into Nicholls's behaviour at a performance in Annandale on Thursday night, where he is accused of malicious damage and assaulting a photographer from The Sun-Herald.

Janie Barrett was taking photographs of the Vines during their gig on Thursday night when Nicholls allegedly kicked directly at her face, damaging camera equipment worth more than $13,000. The photographer had been given approval by the Vines' management to take pictures at the concert.

"It was completely out of the blue," said Barrett yesterday. "I was shocked and stunned, totally flabbergasted when it happened.

"I've never had any violence directed towards me in this way."

Nicholls's antics at the concert, which also involved the singer verbally abusing fans, prompted executives at Triple M, which staged the concert, to permanently ban the Vines' music from being played on their national radio network.

Executives at the station reacted furiously to Nicholls's behaviour, claiming the 26-year-old singer is risking his music career by disrespecting fans and listeners.

"Craig used to work at McDonald's in Hurstville and I won't be surprised if it all goes wrong and he ends up back there asking 'Would you like fries with that?'," said Mike Fitzpatrick, Triple M's program director, who implemented the nationwide ban on all Vines' music, including any future singles.

An internet poll of listeners after the controversial concert revealed 82 per cent of voters didn't want to hear the Vines' music played on Triple M again.

As one of Australia's biggest overseas musical exports, the band has appeared on the cover of US Rolling Stone and headlined major UK music events including the Reading Festival.

Nicholls has long been known for his wild antics, including being banned from the set of The Tonight Show With Jay Leno, the TV chat show in the US, after smashing equipment during rehearsals. The singer has admitted to the media in the US and UK he has used recreational drugs including marijuana.

But friends insist Nicholls's behaviour is not simply designed to boost his fame as a rock 'n' roll rebel. Instead they claim the singer's increasingly erratic behaviour is a sign of stress and mental exhaustion.

"He needs a break," said a source close to the band. "I guess it's his way of showing something's got to give. It's all too much."

EMI, parent company of the band's record label, made a brief statement blaming Nicholls's behaviour on "illness", before cancelling the band's concert scheduled for the Metro on George Street on Friday night. But friends have claimed it's not illness, but mental exhaustion, which is driving Nicholls's increasingly abnormal behaviour.

"Craig is lashing out the only way he knows how," said the friend. "He's trying to tell them he can't take it anymore."

Craig's father Terry, who spoke to The Sun-Herald yesterday at his Blakehurst home, admitted he was worried about his son. "We always worry about our children," he said. But he denied reports Nicholls was suffering from an illness.