Australia coach Justin Langer gave under-fire skipper Tim Paine his "100 percent" support and blasted criticism of Steve Smith as "absolute rubbish" Wednesday after a backlash against their behaviour in the drawn third Test against India in Sydney.

Paine's captaincy has been questioned after he launched an ugly verbal tirade at India's Ravi Ashwin and Smith was accused of foul play after appearing to scuff up batsman Rishabh Pant's guard at the crease during a tense final day.

But an indignant Langer was having none of it.

"Do I have faith in Tim Paine? You have no idea how much faith I have in Tim Paine," he said on a Zoom call.

Australia coach Justin Langer calls allegations of foul play against Steve Smith 'rubbish'
Australia coach Justin Langer calls allegations of foul play against Steve Smith 'rubbish' AFP / DAVID GRAY

"He didn't have his best day, no doubt about that, but after three years he has hardly put a hair out of place.

"He has been outstanding as the Australian captain in everything he does. He had a frustrating day and we have got to cut him some slack, surely."

Wicketkeeper Paine, guilty of dropping three catches on the final day, has apologised and admitted frustration got the better of him when he tried to unsettle Ashwin, who held out for more than three hours for an unbeaten 39 as the tourists salvaged a draw.

Stump microphones picked up Paine making a series of barbs, including calling Ashwin a "dickhead".

India's Ravichandran Ashwin (centre) has words with Australia captain Tim Paine (left) as Australia's Marnus Labuschagne watches during a tense final day in Sydney
India's Ravichandran Ashwin (centre) has words with Australia captain Tim Paine (left) as Australia's Marnus Labuschagne watches during a tense final day in Sydney AFP / DAVID GRAY

Paine had already been fined for dissent after an expletive-laden rant at umpire Paul Wilson on day two, with the incidents undermining Langer's drive to revamp the team's toxic culture after the "Sandpaper-gate" ball-tampering scandal in 2018.

While backing Paine to continue as captain "for some time yet", Langer also acknowledged criticism would come if anyone deviated from the high standards the team now set themselves.

"When you set a standard as high as he does, and we do, we understand we get criticised when you fall below that. It's not what we are about," he said.

"But Tim is an outstanding leader and will continue to be for some time to come yet. He has my 100 percent support."

While backing Paine to continue as captain "for some time yet", Australia's coach Justin Langer  also acknowledged criticism would come if anyone deviated from the high standards the team now set themselves
While backing Paine to continue as captain "for some time yet", Australia's coach Justin Langer also acknowledged criticism would come if anyone deviated from the high standards the team now set themselves AFP / William WEST

Footage of Smith, who was Australia's captain during the sandpaper scandal and banned for year, suggested he deliberately interfered with Pant's batting guard -- a mark made at the crease to know where your feet are in relation to the wicket behind you.

The number four is renowned for his quirks, including shadow-batting while fielding, and strongly denied doing anything wrong.

"As for Steve Smith, I literally cannot believe some of the rubbish I've read -- absolute load of rubbish," said Langer.

He took particular aim at England greats Michael Vaughan and Darren Gough, personally phoning them after they criticised Smith.

"I've actually spoken to Darren Gough about it and rang him last night," he told sports radio station SEN.

"I spoke to Michael Vaughan as well, I thought he was out of line actually.

"You get it from (some of the critics), but I don't expect it from (someone like Vaughan)."

He added that Smith was well known for his offbeat habits.

"Anyone who suggests for one millisecond he was trying to do something untoward, they're way out of line," he said.

"On that wicket, that was that flat, and it was like concrete, you'd need 15-inch spikes to make an indent on the crease and he went nowhere near the crease.

"So seriously, I thought that was absolutely ludicrous."

The fourth and final Test gets under way on Friday in Brisbane, with the series locked at 1-1.