Johannesburg - In a shocking turn of events, Darren Lehmann has stepped down as coach of the Australian cricket team.

Stand-in Australian captain Tim Paine had been expected to address media at the Wanderers on Thursday ahead of the fourth Test against the Proteas, but instead Lehmann arrived and delivered the news.

Lehmann had told Australian media on Wednesday that he had no knowledge of the ball-tampering plans before they unfolded at Newlands, and added that he would be staying on as coach.

Cricket Australia (CA) CEO James Sutherland had also confirmed that Lehmann would be staying on to serve his contract until the end of the 2019 Cricket World Cup.

It made Thursday's resignation all the more surprising as Lehmann broke down into tears as he delivered the announcement.

The 48-year-old said he had not been pushed into the decision by Cricket Australia and that it was all his own doing.

He said seeing footage of former captain Steve Smith breaking down at a press conference in Australia on Thursday morning had helped him come to the decision.

It was time, Lehmann added, for Australian cricket to move forward under new leadership.

Lehmann will remain coach for the Wanderers Test in what will be his last match in charge.

"This will be my last Test as head coach of the Australian cricket team as I'm stepping down," Lehmann said, reading from a statement.

"After seeing events in the media today with Steve Smith and Cameron Bancroft, the feeling is that Australian cricket needs to move forward and this is the right thing to do.

"I really felt for Steve as I saw him crying in front of the media and all the players are hurting.

"As I've said before, I had no prior knowledge of what happened earlier and do not condone it at all, but good people can make mistakes.

It was before talking about his family that Lehmann began to choke up.

"My family and I have copped a lot of abuse over the past week and it has taken its toll," he said.

"Life on the road means a lot of time away from loved ones and after speaking to my family at length over the last few days, this is the right time to step away.

"I am ultimately responsible for the culture of the team and I have been thinking about my position for a while. Despite telling media yesterday that I'm not resigning, after viewing Steve and Cameron's hurting it is only fair that I make this decision.

"This will allow Cricket Australia to complete a full review into the culture of the team and allow them to implement changes to regain the trust of the Australian public.

"It's the right thing to do."

Lehmann thanked his wife and children for all of their support over the past five years, as well as extending his gratitude to the players and management.

"It's been a wonderful experience," he said.

"Telling the players was the toughest thing I have ever had to do."