Wallabies captain Michael Hooper was "shocked" to learn of claims the Australian rugby union team had been investigated for match fixing after losing a Test they'd been favoured to win.

A report in the Sydney Morning Herald on Thursday night suggested the Wallabies were probed for match fixing several years ago and that a sporting official had recommended the investigation be re-opened.

While the report didn't specify the particular match, or suggest the Wallabies fixed any game on Hooper's watch, the incumbent skipper said he and national teammates had never given anything less than their best efforts while wearing the gold jumper.

"You can't give more than a 100 (per cent)," Hooper said on Friday.

"That's the way I'm built and the guys I've played with have all been cut from the same cloth and I can speak on behalf of the guys I've played with for sure."

The report alleged there was a "deep concern" about a Wallabies loss and there had been suspicious activity in a Test the Wallabies were widely expected to win.

Rugby Australia released a statement on Friday, denying any such investigation was conducted.

"A headline attached to a report in the Sydney Morning Herald today suggested Rugby Australia had investigated a Wallabies Test match "from several years ago" in relation to the possibility of match fixing," the statement said.

"Rugby Australia wishes to confirm it has seen no evidence in regards to inappropriate betting activity or match fixing and has no record of any such investigation occurring in the past.

"Rugby Australia takes any allegation of match fixing very seriously and would always thoroughly investigate should any person or entity ever provide information to the Integrity Unit."

A ferocious competitor and dual John Eales Medallist as Australia's player of the year, Hooper was horrified by the allegations.

"I saw that last night and was shocked," the champion flanker said.

"And then I've seen Rugby Australia's comment this morning and that puts it to bed really.

"So (I'm) not really (surprised or offended), no - not really thinking about that.

"It's just come out. I'm not focusing on it too much. I hope there's nothing to it."

Australia's Rugby Union Players' Association issued a sternly worded statement on Friday afternoon, slamming the "unsubstantiated" claims of match fixing.

"RUPA is extremely disappointed by the unsubstantiated allegations raised in this morning's Sydney Morning Herald, bringing into question the integrity of all players to have worn the Wallaby jersey," it said.

"RUPA remains at all times committed to ensuring the utmost integrity of all sporting contests, and as such, we implore anybody with any evidence of impropriety to immediately report it to Rugby Australia.

"If not in possession of such evidence, we ask those involved to cease slandering the names and reputation of players through reporting in a rumour-mongering fashion."