The competition tsar says Transurban holds a near-monopoly over toll roads in Sydney, leaving it to weigh up whether motorists would be better off if a competitor gained a majority stake in the $16.8 billion WestConnex toll road project.

The Australian Competition and Consumer Commission's initial concerns about a Transurban-led consortium taking control of WestConnex threaten to complicate the Berejiklian government's privatisation of the toll road project within the next three months.

The ACCC has concerns about Transurban gaining majority control of WestConnex. Credit:Steven Siewert

Releasing its preliminary competition concerns, ACCC chairman Rod Sims said the two key issues to be canvassed over the next two months were whether an alternative owner of WestConnex could deliver cheaper tolls or better service for motorists, and if Transurban’s ownership of the new toll road would give it an advantage when bidding to build future motorway projects.

“It is competition for both the building of a toll road and the operation of toll roads that we are looking at. We are taking it very seriously,” he said.