Steve Smith (right) will miss the fourth Test against South Africa while the ICC says it hopes Cameron Bancroft (left) has learned from his mistake

Australia captain Steve Smith has been banned for one match and fined his entire match fee by cricket's world governing body for his part in a ball-tampering incident in South Africa.

Smith said the team's "leadership group" had a plan, carried out by Cameron Bancroft, to tamper with the ball to "get an advantage".

Smith, 28, will now miss the fourth and final Test of the series.

Bancroft, 25, was fined 75% of his match fee and got three demerit points.

Smith admitted a charge of conduct "of a serious nature that is contrary to the spirit of the game", said a statement external-link from the International Cricket Council (ICC).

"As captain, Steve Smith must take full responsibility for the actions of his players and it is appropriate that he be suspended," said ICC chief executive David Richardson.

Hours later, the Australians lost 10 wickets in the final session of day four to lose the third Test by 322 runs.

Chasing a target of 430, they reached 47-0 at tea but were all out for 107. Smith had made one when he top-edged Kagiso Rabada for six, but soon departed for seven.

South Africa fast bowler Morne Morkel, who will retire from international cricket at the end of the series, took the final wicket to finish with 5-23 as the hosts took a 2-1 series lead.

The final match of the ill-tempered series begins in Johannesburg on Friday.

'The game needs to have a hard look at itself'

The ball-tampering incident took place on the third day in Cape Town - escalating the tension around what has been an ill-tempered series.

Television footage showed Bancroft take what he said was yellow tape out of his trouser pocket before rubbing the ball.

Smith said after play it was a "big mistake" but that he would not stand down.

Cricket Australia (CA) has begun an investigation into the actions of its team, which Australia's prime minister Malcolm Turnbull said had "shocked and bitterly disappointed" him.

"The game needs to have a hard look at itself," added ICC chief Richardson.

"The ICC needs to do more to prevent poor behaviour and better police the spirit of the game, defining more clearly what is expected of players and enforcing the regulations in a consistent fashion.

"In addition, and most importantly, member countries need to show more accountability for their teams' conduct.

"Winning is important but not at the expense of the spirit of the game which is intrinsic and precious to the sport of cricket. We have to raise the bar across all areas."

Former England batsman Kevin Pietersen gives his view on the positions of Australia coach Darren Lehmann and his assistant David Saker

Batsman Bancroft admitted "changing the condition of the ball in breach of clause 41.3" and accepted his punishment from Andy Pycroft, who is on the elite panel of ICC match referees.

"To carry a foreign object on to the field of play with the intention of changing the condition of the ball to gain an unfair advantage over your opponent is against not only the laws, but the spirit of the game as well," said Pycroft.

"That said, I acknowledge Cameron has accepted responsibility for his actions by pleading guilty to the charge and apologising publicly.

"As a young player starting out in international cricket, I hope the lessons learned from this episode will strongly influence the way he plays the game during the rest of his career."

Players who accumulate four demerit points in a two-year period receive a one-match ban, while those who get eight in the same 24-month period are banned for two matches.

Neither Smith nor Bancroft had any demerit points on their records before this incident.

Prior to the start of the fourth day's play, CA chief executive James Sutherland said Smith and David Warner had "agreed to stand down as captain and vice-captain respectively for the remainder of this Test match".

Wicketkeeper Tim Paine was appointed acting captain for the rest of the match, though Smith and Warner continued to play.

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

"Cricket Australia and Australian cricket fans expect certain standards of conduct from cricketers representing our country, and on this occasion these standards have not been met.

"All Australians, like us, want answers and we will keep you updated on our findings, as a matter of priority."

CA's head of integrity Iain Roy and head of team performance Pat Howard have travelled to Australia to, according to Sutherland, "gather the relevant information CA need to address this matter and understand it better".

Prime minister 'shocked and disappointed'

Australia's prime minister has also spoken about the issue.

Australian cheating beyond belief - PM Turnbull

"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."

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 punished by the ICC for 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.

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 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 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."

Former Australia fast bowler Jason Gillespie said on Sky Sports: "What we're hearing is at least one senior player is absolutely mortified they have been drawn into this. What we need to establish is who is the leadership group.

"It's hard to think there isn't going to be a fall-out and a big change in personnel. It appears there's going to be some big changes on and off the field.

"The Australia side has to have a deep reflection on how they go about the game, how they're perceived in the wider cricketing world. That perception isn't good, that's the brutal reality."

Renowned Australian cricket commentator Jim Maxwell got emotional talking on ABC Grandstand about the ball-tampering issue at the start of the fourth day.

"I do not remember being as disappointed in an Australian team as I feel and I know a number of Australians and colleagues would feel at the moment," he said.

"It was so blatant and stupid. It was hugely disappointing."

Vaughan and Maxwell have commentated for Test Match Special together

Former England captain Michael Vaughan criticised the "pathetic penalties" handed down to Smith and Bancroft.

In a series of tweets, Vaughan said: "Surely this moment was the time to set a precedent. All the team should be penalised."

Swann critical of 'friendless' Australia

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 third Test.

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 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."

Analysis

BBC cricket correspondent Jonathan Agnew

Ball-tampering has always happened in cricket but it's exceptionally difficult to prove. This time they have someone who has admitted his guilt - he's a captain, the act was premeditated and, worst of all, he has clearly coerced the most inexperienced player in his team to go out and do the dirty work for them, and that's awful.

Australia have very few friends in cricket at the moment. The boorish way in which they've behaved over the years hasn't helped.

The current series between Australia and South Africa has been ill-tempered. There's been bad blood about the way the Australians play the game.

Many in the cricket world will feel a sense of satisfaction today about what they'll see as chickens coming home to roost.

I really think this is an opportunity for the Australian authorities to look very carefully at their game.

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.

His bowling was - and remains - wildly inconsistent, and doubts about his unorthodox batting technique 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 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."

What about the Ashes?

Australia came into the series against South Africa on the back of a convincing 4-0 victory on home soil over England, who are involved in a two-Test series in New Zealand.

England bowler Stuart Broad says he did not sense anything untoward in the defeat in Australia but says it is "strange" Smith's side changed their approach in South Africa.

"We played five Ashes Tests and they reversed it in pretty much all of them, and on drop-in pitches," external-link said Broad.

"So to then change their method on a tour to South Africa in the third Test match seems a slightly strange one."

He added: "There were occasions when they we reverse swinging it when we didn't find the means to be able to do that. We just class that down to home conditions.

"We move the ball differently to different teams in England, and Australia moved it better than we did and out-bowled us in Australia. That's how we saw it.

"Steve has come out and said it's the first time they've ever tried it and we have to believe his words."

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.