Prime Minister Malcolm Turnbull says the Australian cricket team ball tampering scandal is a "shocking disappointment" and he wants the game's governing body to take "decisive action" against the cheaters.

The futures of Test side captain Steve Smith and coach Darren Lehmann hang in the balance after Smith admitted to hatching a plan to tamper with the ball during the third Test against South Africa at the weekend.

Cameron Bancroft used a piece of yellow tape to illegally tamper with the ball, a plan that Smith has admitted was devised by the team's leadership group during the lunch break. This group is also likely to have featured vice-captain David Warner and fast bowlers Mitchell Starc and Josh Hazlewood but, according to Smith, not Lehmann.

Mr Turnbull said Australians woke up "shocked and bitterly disappointed" by the news.