Australia's most celebrated Olympic shooter, Michael Diamond, has fallen out spectacularly with fellow gold medal winner Russell Mark, attacking his former teammate in social media rants that have revealed a bitter split in the sport less than four months before the Rio Games.

The Atlanta and Sydney gold medallist – who wants to carry the flag for Australia at the opening ceremony of what would be his seventh Olympics – is also under fire for appearing to belittle Victorian teenager and fellow Olympic aspirant Mitchell Iles in separate posts on Facebook last month.

Iles, 17, is appealing his non-selection for the Australian team at the Court of Arbitration for Sport, prompting the Australian Olympic Committee to delay the announcement of Diamond and Commonwealth Games gold medallist Adam Vella as Shooting Australia's two entries in the men's trap in Brazil.

As that hearing approaches, Mark on Thursday responded to a vicious social media serve delivered by Diamond against him in February, and slammed his former roommate for "having a go" at the up-and-coming Iles – who could end up being a teammate of Diamond's in Rio – last month.

In two late-night posts since deleted but obtained by Fairfax Media, Diamond calls Mark "an absolute joke", accuses his retired ex-teammate of preying on welfare recipients with his ownership of two pubs in Hoppers Crossing on the outskirts of Melbourne, and disparages his brief stint as a federal Liberal Party candidate in 2001.

"Why don't you fund the junior team you have 2 pubs that you are taking doll recieving clients that walk out of your establishment broke after playing the pokies (gambling) but you have the ordasady to have sat on SA BOARD as an athlete what crap are you trying to bring to all of our sport," Diamond wrote in one of the posts.

In the other he added: "Didn't you run for politics Russell marks and got run out I can recall the moment on TV u ran what did u run for if u had nothing to hide no balls mate. I can't stand two faced fellows like you."

Two of Michael Diamond's Facebook posts.

Last month, while Diamond was in Nicosia, Cyprus, for a world cup shotgun event, he posted a photo of a ring on his wedding-ring finger, with the following comment: "It won't be the only iles il walk."

That was seen as an insult to Iles. Another post, in which Diamond offers his support to Iles, wishing him "all the luck in the world for your appeal" and offering to "donate my time free of charge to excel you further" has also been interpreted by some as a slap in the face to Iles' grandfather and coach Bill, who Mark regards as Australia's greatest coach.

"If you're not a shooter you wouldn't get it, but everyone in the sport got it," Mark said.

Mark, who roomed with Diamond in Atlanta, Sydney and in London after he was not permitted to share accommodation with his wife Lauryn, said he was stunned at the attack on him and the perceived shot at then 16-year-old Iles.

"Michael is obviously feeling the pressure, but I think taking it out on social media on Mitchell or me is not the way to go about it. He is the best competitor I've ever shot against and I was lucky enough to ride on his coat tails, but just because he's a great competitor doesn't mean he's a great person any more," Mark said.

"We obviously aren't rooming together any more. They'd want to disarm us if we were.

"The most disappointing thing is the stuff about Mitch. You've got to remember this is a 16-year-old kid. I'm 52 – I can handle myself. That would have hurt Mitch. Everybody read that and thought, 'What are you doing, Michael? You're having a go at a boy here.' You don't have a go at boys and you certainly don't do it on social media. He would have lost a lot of friends over that. I know they have a social media policy at SA, so I'd be interested to hear what they say."

The attacks on Mark were posted in the days after the Australia Cup 1 event, which ran from February 19 to 21 at the Sydney International Shooting Centre. Diamond failed to show up to complete the men's trap event on the Sunday, after shooting in the first three rounds the previous day.

In a post on the Saturday afternoon, Diamond uploaded a photo of himself with the caption: "Heading to casino lads … Who's up to hang out at sports bar."

When contacted by Fairfax Media on Thursday in Rio, where he is competing at a world cup event, Diamond said of the posts about Mark: "There is nothing untrue about it. What do you want me to say?"

Asked whether he had been drinking at the time of the posts, he replied: "No comment."

SA chief executive Damien Marangon said he had spoken to Diamond about social media standards.

"I've had a conversation with Michael around social media, trying to make sure that not just Michael but all our athletes are aware of this new risk which is social media," Marangon said.

"We have a set of expectations that we would expect from our athletes particularly our athletes who like Michael are supported [financially]."

Mark, who will commentate on shooting events for Channel Seven in Rio, traces Diamond's attack on him back to last year, when he said he advised him against becoming the new shooters' rep on the SA board.

The Facebook posts came in response to the Atlanta double trap champion's public criticism of SA's selection policy. Mark said he was not taking sides in terms of who should be on the men's trap team in Rio.

"I had a go at Michael in August last year when Michael became the shooters' rep, because that's really not him, being an administrator," Mark said. "I said to him, 'They're just using you,' and he took offence to it. So we cut ties then and there.

"It's a bit disappointing for a guy that I was a character witness for at his court case [when Diamond was found not guilty of assaulting a former girlfriend outside a bowling club in 2003]. But at least I know where I stand with him. He was upset at a story where I criticised Shooting Australia's selection policy. I think the young kid has got a case, but Michael obviously thinks the world is against him. I'm not against Michael Diamond – I'm against the policy.

"I believe he deleted [the posts] soon after but 1000 people screen-shot it and I got messages from shooters from all over the world."