Hackett's tell all interview

Grant Hackett is preparing to tell all about his shocking fall from grace.

In an interview with Nine's 60 Minutes, to air Sunday at 7.30pm, the former swimming champ will speak for the first time about the night he violently trashed his apartment in a drunken rage and the collapse of his marriage to singer Candice Alley.

The 32-year-old will also address allegations he physically abused Alley.

As the Nine Network employs Hackett, the interview will be seen as a way to publicly clean up Hackett's reputation before his involvement with their London Olympics coverage, where he will be part of their commentary team.

Yesterday, Alley's dad Emilio Giannarelli publically stated that Australia's Olympic team chief Nick Green should be ashamed of his support for Hackett.

Green had commented he would be happy to appear with Hackett at the Prime Minster's Olympic dinner on Saturday night.

"I don't know him very well but he seems to be a genuine person, and this is out of character," Green said.

"I will certainly extend my hand of friendship to him whenever I see him."

But Giannarelli said Green should be “ashamed” of his comments

"He should be ashamed because he doesn't know the actual circumstances," Giannarelli said.

"No one should be commenting prior to those circumstances coming out.

"I'm devastated by what Grant has put my daughter and my grandchildren through. The pictures that have been published speak for themselves.

"I would like Nick Green to be in my shoes before he makes those sorts of decisions."

Since Hackett split from Alley last month, he has also been dropped as the face of Westpac and as an ambassador for the Alannah and Madeline Foundation, a charity that keeps children safe from violence.