Grant Hackett has been advised to seek help after apologising for his behaviour on the now infamous flight from Adelaide to Melbourne on Sunday morning.

The 35-year-old, who won three Olympic gold medals for Australia, was questioned by federal police at Melbourne Airport but released without charge.

An investigation remains ongoing amid claims he grabbed a man on the chest for reclining his seat and that he had to be restrained by staff.

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While those reports remain unconfirmed, Hackett issued a brief statement on Monday that was full of remorse.

“I seriously and genuinely regret my poor behaviour,” it read.

“I have stuffed up more than once and am working on these issues.

“It is embarrassing to hear and read the consequences of my actions. I apologise unreservedly to the gentleman on the flight. I am trying to make direct contact with him personally.

Huegill is no stranger to trouble himself. Photo: Getty

“I know I have to front the media and discuss my actions in a more appropriate and accountable way. I just have to be as frank and open as I need to be. I apologise for any inconvenience.”

Former swimmer Geoff Huegill – an Olympic medallist for Australia and no stranger to controversy himself – said he thought Hackett needed some time away.

Hackett went to famed rehabilitation facility ‘The Meadows’ in Arizona in the USA in 2014, as he was battling an addiction to sleeping medication Stilnox.

“The only words of advice I can pass onto Grant is to take time out again,” Huegill wrote on Facebook.

“And if it means you need to head away and revisit some of the facilities of the past, then don’t be afraid to put your hand up and say you need help.”

Reports of major on-flight argument denied

Claims that Hackett had “sexually assaulted” his victim by groping him on the chest were published in a News Corp publication.

The flyer, also in business class on the Virgin Australia flight, said: “As I reclined my chair, he grabbed it and yanked it back.

“Then he put his hand through and groped my chest and tweaked my nipple quite forcefully.

“I felt unsafe and violated … then when we began the descent he tried to do it again.”

News Corp reported on Monday evening that Hackett had spoken to the man who would not press charges.

Chief executive of AFL heavyweights Collingwood, Gary Pert, was also a passenger on the flight.

He offered a different version of events on Monday, saying that Hackett was not in a state to be antagonistic.

“He wasn’t aggressive,” Pert told SEN.

Pert admitted Hackett was ‘pretty well passed out’ on the flight. Photo: Getty

“In fact, the majority of the flight he was pretty well passed out.

“There was no rowdy behaviour. He didn’t jump out of his seat. He wasn’t restrained by any of the staff.

“There was no big argument and (after the disagreement) he sat back and went back to sleep again.

“To be quite honest, Grant was quite incapacitated at the time to do much more than be able to tap him.”

Pert also said it was clear that Hackett was in “quite a bit of trouble” and that he had helped him off the plane.

‘You become a recluse because you know you’ve let people down’

Huegill knows more than most how difficult it is to repair one’s image.

He and his wife, Sara, who is a publicist, pleaded guilty to cocaine possession in 2014, while earlier in his career, the swimmer’s life was out of control after he put on 45kg due to a poor diet and use of alcohol and drugs.

“You consistently second guess every relationship or business opportunity and wonder if the challenges of your past are the reasons that block future opportunities,” he said.

“Your mental state is hammered … you become a recluse because you know you’ve let people down.

“The sad thing is that Grant will have to live with this (incident) for the rest of his life.”