Australia captain Tim Paine leapt to the defence of Steve Smith, who was accused of deliberately scuffing away the guard of India batsman Rishabh Pant on a climactic final day of the third Test between the teams.

Smith was filmed on a stump camera shadow batting then seemingly swiping away at pitch marks made by Pant, whose 97 from 118 balls gave India a chance of an unlikely victory in Sydney before they settled for a memorable draw.

The teams head into the final Test, which gets under way at Brisbane later this week, with the series at 1-1 but there is scrutiny on Smith following his conduct at the SCG.

Former India opener Virender Sehwag and England's Ashes 2005-winning captain Michael Vaughan were among those to criticise the actions of Smith, who was sacked as Australia captain for his role in the ball-tampering scandal two years ago.

But Paine, his successor as skipper of the national side, said: "I have spoken to Steve about this, and I know he's really disappointed with the way it's come across.

"He was certainly not changing guard, and I'd imagine if he was then the Indian players would have kicked up a bit of a stink at the time.

"When he's in the field, he likes to walk up to where he bats and visualise how he's going to play. That's something I have seen Steve do many times."

Paine's behaviour as the Test built to a thrilling conclusion was also questioned after a heated verbal exchange with India's Ravichandran Ashwin, who was called a "d*******" by the increasingly-agitated wicketkeeper.

Paine, who was fined 15 per cent of his match fee for showing dissent to an umpire earlier in the Test, dropped three catches behind the stumps on day five.

He has been widely credited with improving Australia's reputation following the ball-tampering saga in Cape Town in 2018 but told reporters in an unscheduled press conference he was unhappy with how he behaved at the SCG.

He said: "I'm someone who prides themselves on the way I lead this team and that was a poor reflection.

"My leadership wasn't good enough, I let the pressure of the game get to me. It affected my mood and then from there affected my performance.

"I said to our players 'I've had a really poor game as a leader'. I let our group down. I'm human, I want to apologise for the mistakes that I made."