Australians caught up in the Volkswagen emissions scandal want the global car giant to "admit they were wrong" in their pursuit of compensation.
Joint class actions against VW and sister companies Audi and Skoda opened in the Federal Court in Sydney on Monday.
The estimated two-week trial was launched by law firm Maurice Blackburn on behalf about 100,000 affected motorists.
It follows revelations in 2015 Volkswagen, Audi and Skoda had fitted their cars with software that could detect test conditions and cut its emissions accordingly to improve results.
The first stage in the VW trial will determine whether the technology is a prohibited "defeat device" under Australian law, lawyer Jason Geisker says.
He argues the company misled customers by selling affected diesel vehicles as environmentally friendly cars.
"VW happily profited for many years off the back of their 'eco-friendly' diesel deception yet, ever since the truth was finally exposed, they have refused to fess up here and take responsibility for people's losses," Mr Geisker said in a statement.
"Motorists want the VW group to admit to their wrongdoing, and motorists understandably expect to be appropriately compensated by the companies for their losses as a result."
In the US and Canada, VW spent nearly $30 billion compensating customers for the same scandal but continue to deny everything in Australia, Mr Geisker says.
VW driver and owner Alister Dalton, the lead plaintiff in the case, says he is disgusted by the company's conduct.
"The way they've tricked us and the way they've treated us since this came to light has been beyond bad - it is the worst customer relations management one could imagine," Mr Dalton said in a statement.
