The NSW opposition says if elected, it would speed up construction of the western Sydney metro by scrapping a different rail project but the government has mocked the proposal.
Labor leader Luke Foley on Friday said he would cancel the government's planned metro conversion of the Sydenham to Bankstown rail line if elected in March 2019.
The opposition would instead prioritise the Sydney Metro West project linking Parramatta to the CBD.
Mr Foley said by scrapping the Sydenham to Bankstown rail conversion - as well ditching the coalition's planned northern beaches road tunnel - a Labor government would have the funds to fast-track by "years" the western Sydney metro.
"Government is all about priorities and Labor's priority is to deliver better transport links between western Sydney - soon to be home to three million people - and Sydney's CBD," Mr Foley said in a statement.
"Today's announcement clearly lays out Labor's top transport priority and builds on an earlier commitment to not proceed with the construction of a hugely expensive mega road tunnel to the Northern Beaches."
But Transport Minister Andrew Constance attacked Labor's announcement describing it as a "smoke and mirrors trick".
"Cancelling projects and contracts isn't a policy, it's a debacle," Mr Constance said in a statement.
"No one has forgotten Labor's empty transport promises and thankfully today everyone's been reminded again it's the party of cancellation, not construction."