Sydney (AFP) - Police released troubled Australian swimming star Grant Hackett without charge on Wednesday as the Olympic gold medallist's family voiced fears for his mental health.

The fallen star's father Neville called police to their home at Southport on the Gold Coast after a bout of heavy drinking led to "uncontrollable rage", the Gold Coast Bulletin reported.

"Grant's got a medical problem and it manifested itself here this morning... he was raving and ranting a bit," Neville told the newspaper. "It's what I'd call a bit of a breakdown."

The 36-year-old in 2014 came out of six years of troubled retirement to try to make the Rio Games, hoping to become the oldest Australian swimmer to qualify for an Olympics.

But he narrowly missed out on an Olympic place and last April hit the headlines again after a meltdown on a plane.

He vowed to quit the bottle after being accused of drunkenly squeezing the nipple of a fellow business-class passenger on a flight from Adelaide, where the Olympic swimming trials were held.

Hackett admitted he had been binge-drinking and apologised to the man whose nipple he pinched.

"This is now a chronic problem... so, from a mental health perspective, I hope something can be done," Hackett's brother Craig told reporters.

"This is not Grant Hackett, this is a completely different person. I don't know this person, my mum and dad don't know this person.

"He's there in body, but he is not there in mind, in soul, or spirit," he said.

Hackett, one of the greats of Australian swimming, retired after the 2008 Beijing Olympics, having won the 1500m freestyle in both the 2000 Sydney and 2004 Athens Olympics.

He also claimed four world titles in the 30-lap event.