Steve Smith and David Warner have stood down as leaders for the rest of the third Test over the ball-tampering bombshell, with Tim Paine now leading Australia in Cape Town.

Captain Smith and vice-captain Warner took the field under Paine's leadership at Newlands, where the tourists were booed onto the field as day four started on Sunday.

The board of Cricket Australia (CA) is yet to make a decision on what to do with Smith and Warner, who are both under immense pressure to relinquish their leadership posts.

Smith confessed overnight that Australia's leadership group authorised premeditated cheating at Newlands, wanting to use sticky tape in an illegal attempt to change the condition of the ball.

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"This Test match needs to proceed, and in the interim we will continue to investigate this matter with the urgency that it demands," CA chief executive James Sutherland said.

Smith travelled to the ground on the team bus on Sunday then sequestered himself from the team.

Smith's 10 ashen-faced teammates all went through their standard pre-play routines on the morning of day four but their leader was nowhere to be seen.

The gifted batsman is likely to be charged by the International Cricket Council but the prospect of more stern punishments loom large.

"I won't be considering stepping down. I still think I'm the right person for the job," Smith told reporters after day three.

Senior members of the side hatched the idea of using tape, which they hoped would capture debris from the pitch and scuff one side of the ball, at lunch on day three.

Cameron Bancroft used the tape while working on the ball in the post-lunch session then attempted to hide it from umpires. Bancroft has been charged with ball tampering by the match referee.

The ugly episode has prompted an outpouring of shock and condemnation, with the Australian Sports Commission leading calls for Smith and "any other members of the team leadership group or coaching staff who had prior awareness" to be stood down.

"I've spoken with David Peever, the chairman of Cricket Australia, a few moments ago and I've expressed to him very clearly and unequivocally my disappointment and my concern," Prime Minister Malcolm Turnbull said.

CA has dispatched team performance chief Pat Howard and head of integrity Iain Roy to conduct a full investigation of the saga.

"Today was a big mistake," Smith said. "I take responsibility as the captain. I need to take control of the ship.

"I'm incredibly sorry for trying to bring the game into disrepute the way we did.

"This is certainly something I'm not proud of and something that I can hope to learn from and come back strong from."

The skipper wouldn't divulge the other teammates involved in the discussion. The leadership group has featured Mitchell Starc and Josh Hazlewood in the past.

Smith insisted coaching staff, including Darren Lehmann, were not aware of the premeditated plan and that his side have never tried using tape to scuff the ball before.

Smith, with the exception of a couple of incidents on a spiteful tour of India last year, had enjoyed a squeaky-clean start to his century-laden captaincy.