Shane Warne has dismissed Australia's struggling Test side as "ordinary" and said they needed a ‘kick up the backside’ after their series flop against Pakistan.

Australia suffered a 373-run defeat against Pakistan in the second of the two-Test series last week after a familiar batting collapse, following a fightback to secure a draw in the first Test.

"It's been pretty ordinary, hasn't it?" the Australian spin legend told reporters on Monday. "We all support the Aussie side as we do but they need a kick up the backside at the moment because they're not performing well."

Warne also took aim at Mitchell Marsh, questioning why he was selected as vice-captain.

"I hadn't even thought before that series that he had established himself in the team," Warne said. "I don't think he's cemented a spot and that's why it was a strange selection for me as vice-captain. He only averages 25 or 26 in Test cricket.”

 The outspoken cricket great said he was a "huge fan" of the Marsh brothers Mitchell and Shaun, but that ‘they need to perform’.

"Mitchell Marsh needs to go and make some runs," he added. "If Mitchell Marsh comes out and makes some hundreds, pick him. If Shaun Marsh makes some hundreds, pick him. If they don't, then pick the guys who are in form."

Warne told the Australian Broadcasting Corporation on Tuesday that cricket in Australia, left reeling by a ball-tampering scandal earlier this year, was struggling and needed to return to its grassroots.

"I think in any business you need the foundation to be strong, and the foundation of Australian cricket has always been grassroots cricket, club cricket, and first-class cricket, Sheffield Shield cricket," he said.

Warne added: I don't think there's enough first-class cricketers getting into school cricket and inspiring people and talking to young boys and girls to say cricket's a great game and this is why, teaching them techniques.  It just doesn't happen anymore.