NSW Premier Gladys Berejiklian should halt Sydney's $16.8 billion WestConnex road project after a national auditor-general's report found major flaws in the way the project was funded, opponents say.

The Australian National Audit Office report, released on Tuesday, found that an upfront payment by the federal government and the approach to agreeing milestones for later payments “did not adequately protect the Australian government’s financial interests”. Both Labor and the coalition in Canberra committed at least $1.5 billion in grant…