Federal Opposition Leader Bill Shorten has confirmed a Labor government would honour the Commonwealth's funding commitment to the WestConnex project.

Mr Shorten clarified Labor's position after the Federal Government seized on comments made by the Opposition's Transport and Infrastructure spokesman, Anthony Albanese, at a community meeting over a week ago, that Labor would not provide any money for the construction of the 33-kilometre motorway.

The $16.8 billion project to widen the M4 and connect it to an extended M5 is unpopular in Mr Albanese's electorate of Grayndler in Sydney's inner west. The seat is also being challenged by Greens candidate Jim Casey, who opposes WestConnex.

The Commonwealth has committed a $2 billion loan and a $1.5 billion grant for the construction of the motorway.

Federal Minister for Major Projects Paul Fletcher said not all of the $3.5 billion had been handed over, so that money would be in jeopardy if Labor won the election.

"More than $2 billion of this remains to be paid, and if Mr Albanese becomes the Minister, he has said not one federal dollar for WestConnex ... so this is bad news for the people of western and south-west Sydney," he said.

"They're turning their backs on the people of western and south-west Sydney and on this vital project and it's because Mr Shorten and Mr Albanese are chasing inner-city Greens votes in electorates like Grayndler."

But Mr Shorten said the federal funding had been finalised and he would not change the agreement if Labor won the election.

"The funding has already gone and Labor won't repudiate any contracts, full stop," he said.

"We do support WestConnex. We're determined to act on the congestion which confronts motorists and workers coming from the western suburbs to Sydney every day.

"But we have also said, both Anthony and I, that the WestConnex project isn't satisfactory in that it doesn't go to the port and the city. We've also said that the communities affected by it should be diligently consulted."

Yesterday, several thousand people gathered at Sydney's Town Hall to voice their concerns over a number of city projects, including the WestConnex freeway.