Smith first captained Australia in December 2014, and took the role full-time when Michael Clarke retired after the 2015 Ashes in England

Australia captain Steve Smith must be immediately removed from his role over the ball-tampering row in South Africa, an Australian government agency says.

Smith said on Saturday that the team's "leadership group" had spoken about a plan to tamper with the ball, carried out by batsman Cameron Bancroft.

The Australian Sports Commission (ASC) has now called for Smith "to be stood down immediately, along with any other members of the team leadership group or coaching staff who had prior awareness of, or involvement in, the plan".

The incident took place on the third day of the third Test between South Africa and Australia in Cape Town - escalating the tension around what has been an ill-tempered series.

The ASC statement added: "This [Smith's removal] can occur while Cricket Australia completes a full investigation. The ASC condemns cheating of any form in sport. The ASC expects and requires that Australian teams and athletes demonstrate unimpeachable integrity in representing our country."

Earlier, Cricket Australia (CA) chief executive officer James Sutherland announced that such an investigation would now take place - with CA's head of integrity Iain Roy and head of team performance Pat Howard travelling to South Africa to "gather relevant information" - but that Smith would remain as skipper for now.

Why does the condition of the ball matter?

Umpires have the power to change the ball and award five penalty runs to the batting side if they feel it has been altered illegally - although they did not do so in this case

Bancroft has been charged by the International Cricket Council (ICC) with attempting to change the condition of the ball - which is prohibited by Law 41.3. external-link

Roughing up one side of the ball can help the fielding side achieve "reverse swing" - in which the ball moves in the opposite direction to conventional swing, which is achieved by polishing one side of the ball.

There are several methods by which the ball can be deliberately roughed up - ranging from the outright illegal (scuffing it with a bottle top, or scratching with fingernails), to those which are frowned upon but frequently take place anyway, such as throwing the ball into the stumps on the bounce, or applying saliva after sucking sugary sweets.

Polishing the ball on your clothing is allowed if no artificial substance is used, as is drying a wet ball with a towel that has been approved by the umpires, or removing mud from the ball under an umpire's supervision.

The umpire's ultimate sanction, if they feel the ball has been altered illegally, is to change the ball and award five penalty runs to the batting side - although this did not take place in Cape Town.

Such an instance did take place at The Oval in 2006 when umpires Darrell Hair and Billy Doctrove ruled that Pakistan had tampered with the ball during a Test against England. Pakistan refused to take the field after tea in protest, and forfeited the Test.

Current South Africa captain Faf du Plessis has also had two major run-ins with the authorities over ball-tampering.

In 2013, he was caught on camera rubbing the ball against a zip on his trouser pocket in a Test in Dubai, which earned Pakistan five penalty runs and a change of ball, and Du Plessis a fine.

Three years later in Hobart, Australia were incensed when TV footage appeared to show Du Plessis licking his finger and shining the ball while eating a sweet - which cost him his match fee.

Prime Minister 'shocked and disappointed'

Less than 24 hours after Bancroft was caught by the cameras taking what he said was yellow tape out of his trouser pocket before rubbing the ball, the row had escalated enough for Australian Prime Minister Malcolm Turnbull to speak out about the issue.

"I am shocked and bitterly disappointed by the news from South Africa," said Turnbull.

"It seems beyond belief the Australian cricket team have been involved in cheating. Our cricketers are role models and cricket is synonymous with fair play. How can our team be engaged in cheating like this? It beggars belief."

Turnbull later added: "I have spoken with David Peever, the chairman of Cricket Australia, and I have expressed to him very clearly and unequivocally my disappointment and concern. He has said to me that Cricket Australia will be responding decisively, as they should.

"It's their responsibility to deal with it, but I have to say that the whole nation, who hold those who wear the baggy green up on a pedestal - about as high as you can get in Australia, certainly higher than any politician, that's for sure - this is a shocking disappointment."

Watch: Bancroft and Smith admit ball-tampering plan

Former players condemn 'premeditated cheating'

Michael Clarke, Smith's immediate predecessor as Test captain, called it "a terrible day for Australian cricket", described the plan as "premeditated cheating" and condemned its instigators for choosing rookie batsman Bancroft to carry it out.

"I can't believe the leadership group have got a young kid playing in his eighth Test match to do this," Clarke told Australia's Channel Nine.

"We have got the best bowling attack in the world. We don't need to cheat to beat anyone."

Clarke retired from international cricket in 2015 after suffering with a chronic back problem for many years, but when asked whether he would consider a shock return if Smith were to depart, he replied: "If I was asked by the right people, then I would think about my answer."

Former Test vice-captain Adam Gilchrist told BBC Radio 5 live that he was "stunned and shocked... embarrassed and sad".

The legendary wicketkeeper said: "Australian cricket is the laughing stock of the sporting world.

"I remember being a current player and the last thing you wanted was ex-players putting the boot in, but I have the feeling we have been all really badly let down here.

"The only positive is that they admitted it. We'll get stories now where it will be 'oh, all teams do it, in different levels and different ways'. But it's not bending the spirit of the game, it's going outside the laws. It's not acceptable."

Players have clashed during a bad-tempered series - notably Quinton de Kock and David Warner, who were both sanctioned by the ICC after the first Test

Australia 'playing under siege mentality' after fiery series

The South Africa-Australia series had already contained several flashpoints before the sides arrived in Cape Town for the current third Test.

Smith's vice-captain David Warner had to be restrained by team-mates during an off-field altercation with Proteas wicketkeeper Quinton de Kock during the first Test in Durban, for which both players were fined by the ICC and given demerit points.

South Africa pace bowler Kagiso Rabada was then handed a two-match suspension after deliberately brushing shoulders with Smith after celebrating his dismissal in the second Test at Port Elizabeth, but won an appeal to reduce his punishment to one demerit point rather than two, meaning he avoided a ban but remains one point away from it being triggered.

Australia coach Darren Lehmann then hit out at what he described as "disgraceful" verbal abuse towards his side in the early stages of the Cape Town Test.

"The Australian team have been playing under a siege mentality," ABC commentator Adam Collins told BBC Test Match Special.

"Lehmann had complained about the treatment the players have been getting - they are furious about what has happened in the last couple of weeks. Steve Smith is not a bad bloke. There is something else going on here.

"But the response on social media is very strong. It is trending against Steve Smith - it's not as if people are defending him. Smith knows he is in a lot of trouble.

"Australian fans would rather see their team lose than win like this."

Part-time spinner to Bradman comparisons - the rise of Steve Smith

Smith made his Test debut against Pakistan in 2010, in a neutral series played in England

The blond quiff has flattened and darkened somewhat over the years, and on the field Steve Smith is almost unrecognisable from the raw 21-year-old who made his Test debut against Pakistan at Lord's in July 2010.

Selected primarily for his leg-spin bowling, Smith made one and 12 batting at number eight and nine in that game. He made two half-centuries in his first 10 Test innings, but was dropped after Australia lost the 2010-11 Ashes to England.

While his bowling was - and remains - wildly inconsistent, it was doubts about his unorthodox batting technique that meant he was out of the Test side for two years.

But on his return, he slowly became such an integral part of the side that at 26, he was the natural successor to Michael Clarke as captain in 2015, while his batting statistics soared to the point where hesitant comparisons were drawn with Australia legend Sir Donald Bradman.

Passing the 1,000-run mark in the past four calendar years, he was at the top of his game in the 2017-18 Ashes against England, hitting a career-best 239 as skipper at Perth to regain the urn, and averaging an incredible 137.40 across the five Tests to sit at the top of the ICC's batting rankings.

Yet his rise has not been without controversy. In March 2017, India were angered after Smith looked up to the dressing room while pondering whether to review an lbw decision - contrary to ICC regulations that outlaw off-field assistance.

And his Australia side's behaviour has been increasingly questioned, with senior Australian radio commentator Jim Maxwell commenting: "I've started to become more and more offended by the arrogance of some of the players in the way they behave."

And finally... Bancroft's tweet comes back to haunt him

Meanwhile, the social media world has picked up on a tweet Bancroft sent in 2013 - with England women's spinner Alex Hartley among those to notice.