Australia batsman Cameron Bancroft has admitted to trying to change the condition of the ball using a foreign object on the third day of the Cape Town Test against South Africa.

"I had discussions with the match officials, I've been charged with attempting to change the condition of the ball," Bancroft, 25, said after play in Cape Town. "We had a discussion during the [lunch] break and I saw an opportunity to use some tape, get some granules from the rough patches on the wickets and change the condition, it didn't work, the umpires didn't change the ball. I was sighted on the screen and that resulted in me shoving it down my trousers."

The incident took place during the afternoon session and was picked up on by TV cameras. A small, yellow object was seen in Bancroft's hands after he had worked on the ball, and he was also captured taking it from his pocket and placing it down his trousers. The footage showed Bancroft rubbing the rough side of the ball, the opposite side to which he would usually be trying to shine on his trousers. He put the object down his pants apparently after being spoken to by the substitute Peter Handscomb, who had come on to the field after speaking to coach Darren Lehmann over walkie talkie. Lehmann seemed to speak to Handscomb after footage of Bancroft working on the ball was shown on the TV screens at the ground.

The umpires Nigel Llong and Richard Illingworth were then seen speaking with Bancroft, though they did not choose to change the ball or penalise the Australians five runs - the statutory on-field penalty for illegally changing the condition of the ball.

When Bancroft spoke to the umpires, he was shown holding a bigger, black cloth rather than the small yellow object he had earlier seemed to place down his trousers. Both South African and Australian commentators on the host broadcaster, SuperSport, said Bancroft's actions looked suspicious. "It is very suspicious. There is no doubt about that," Allan Border said at the time. "If you're caught doing the wrong thing, you've got to pay the penalty."

The former South Africa captain Graeme Smith said he was surprised the umpires had not changed the ball. "In my opinion I think he's tampered with the ball and used an object to do that," Smith said. "It does look like it's a bit of sandpaper. The footage doesn't look good. I'm quite amazed the umpires haven't done anything with the ball. The footage is quite damning.

"If it is proved that what has gone on in the footage is correct then some tough questions have to be asked of Steve Smith and Darren Lehmann. I think there is a lot of questions that need to be answered and Australia need to answer them. For me it's quite obvious that he's doing something with the ball and the umpires need to do something about it."