Bill Shorten’s pledge to spend $3 billion on a Metro West line between Parramatta and central Sydney has triggered an about-face from Transport Minister Andrew Constance, who has stopped calling on the federal government to help fund the project.

Mr Constance has consistently appealed for federal funds to pay for the rail line, which is badly needed to alleviate pressure on Sydney's over-crowded western rail line.

NSW Transport Minister Andrew Constance. Credit:Janie Barrett

“Canberra need to seriously start to look at this project to make this work" Mr Constance told the Herald on Thursday. "If I can get Canberra also interested in this it has the potential to be even more fantastic,” he said of a rail project he has championed.

But after Labor leader Mr Shorten promised $3 billion for the project on Sunday, Mr Constance, while alongside his federal Coalition counterpart Paul Fletcher on Monday, repeatedly declined to advocate for funds.