Pat Cummins flatly denied Usman Khawaja's claims that the entire Australian cricket team was implicated in the 2018 sandpaper scandal, saying at a press conference in Sydney the allegations were "complete and utter nonsense"and "100% wrong".

The Test captain's defiant appearance on Friday morning prompted David Warner to later accuse Cummins of throwing Khawaja under the bus as the feud engulfing Australian cricket continued.

Appearing before dozens of reporters and cameras at Cricket New South Wales' headquarters and fielding questions for more than an hour, Cummins denied the allegations aired in his former teammate's book, Sabr, and said he had no knowledge of the ball tampering plot in South Africa.

Australia's captain at the time, Steve Smith, then vice-captain, Warner, and opener Cameron Bancroft were handed long suspensions by Cricket Australia (CA) after the governing body's short investigation into the incident.

Khawaja alleges in his memoir that more than just the three banned players were aware of the team's ball-tampering plans, and that sandpaper was also used on the ball during the preceding Test. The former Australia batter has called for "all" of the team to take collective responsibility.

Cummins said Khawaja was a friend to him, adding he had been "grappling" over recent days as to whether their relationship was irrevocably harmed.

He said Khawaja was "100% wrong" with his claim that the whole team knew sandpaper was going out on the field, maintaining he "did not know that was happening" and "did not see anything on the ball" at the time.

"He says that I and others were architects of a scheme to ball tamper with sandpaper. That's complete and utter nonsense," Cummins said.

"I was genuinely shocked this week when I found out Usman admitted he told Cam [Bancroft] to be careful when using sandpaper. That's not [the] Usman that I know. It's not the Usman that has been part of the team that's helped rebuild the Australian cricket culture over the last eight years.

"Usman is a friend, but friends aren't casual with each other's lives and reputations. In his book he's been casual with my life and the lives of many others and, I think, Australian cricket."

Cummins said there was "no masterplan around using illegal methods".

"I think that's maybe something that hasn't been spoken about enough," he said.

"People assume you have gone from very legal methods to suddenly taking sandpaper and then must have been some huge masterplan. That is not the case. There's no grand plan, there's no bowlers saying, 'this is what must happen.'"

Warner appeared in his capacity as a commentator on Kayo soon after the press conference in Sydney wrapped up and said he stood by Khawaja's account in the book.

"I actually feel for him [Khawaja] at the moment," Warner said. "I actually feel that the captain today threw Uzzy under the bus and I'm very disappointed by that.

"For me, it's about accepting the truth, and I just don't think this will rest. I'm still getting called the architect, the fixer, and all this kind of stuff – and it really, really hurts.

"But it's also affected ... the Australian cricket team. So it's important for us to allow us time to heal it, but until the truth is accepted, it's going to be very, very difficult to move on."

Cummins did concede that the 2018 Australian men's team had a "win-at-all-cost mentality" and an "ugly underbelly" which he said he had tried to eradicate in his past six years as captain.

"I thought that the way we acted on the field was quite abrasive. I didn't like the way we spoke to umpires, the opposition," he said.

"I think there was a bit of an arrogance and a bit of an ugliness at times that didn't sit well with me as a young guy. And now I'm captain, I have spent a lot of time making sure that that's not the case with this current Aussie team."

Cummins said he had texted with Khawaja briefly since his memoir was released on Tuesday but didn't delve into the nature of their correspondence.

He said "some of" the claims in his memoir were "probably true … and they are his accounts of what happened", but added there were "a few big leaps here where he's being vague".

"Perhaps there was conversations with Cameron Bancroft around taking sandpaper out and how to do it," he said. "That doesn't mean that everyone in that dressing room knew what was going on.

"If we are talking about how [the players] were sanctioned, my personal opinion was it was way too heavy-handed … But to then extrapolate that out into everyone else knew … that's very different to what I think was injustice."

He also rejected Khawaja's testimony in Sabr that he wasn't picked as Australian team captain – after Smith and Warner stepped – down because of racism.

Khawaja wrote he was "flabbergasted" when Tim Paine was named interim captain, and alleged CA wasn't ready for a "brown Australian cricket captain".

"I think of all the things I've read this week, I think that's actually the most serious," Cummins said.

"I agree with Uzzy on a lot of things, but … him saying that if you're Australian captain you have to be a certain skin colour, I couldn't disagree with that statement any more."

Asked whether he was considering taking legal action for the claims aired in the book, Cummins said he had received advice this week that some of the allegations he made were "probably defamatory", but said "I won't be doing that".

"You've got to move on," he said. "It's been eight years … You got to draw the line at some point. I won't be doing that."

Khawaja has been contacted for comment.