Malcolm Turnbull has announced $5bn for a Melbourne airport train line, a project that has been debated and reviewed by successive state governments for decades.

The prime minister made the announcement on Thursday morning and said the federal money would pay for half and the Victorian government would need to contribute another $5bn.

The only public transport option to and from the airport is the Sky Bus, an express bus service between the airport and the city which can take up to 45 minutes.

“Melbourne’s airport needs a railway,” Turnbull said. “The freeway is getting more congested. Too many Melburnians and visitors spend too many hours stuck in traffic trying to get to and from this airport.

“Other great cities, most great cities with big airports, have railway linkages. Melbourne has been left behind by failures to make decisions about investment in this railway.”

In 2016 the Victorian premier, Daniel Andrews, said an airport rail link was not high on the government’s list of priorities. By November last year, Andrews said a plan for the rail line was on the Victorian Chamber of Commerce and Industry’s wish-list, but it should be “much more” than a link between the city and the airport and would need to take in other suburbs.

Andrews also said last year that he hoped a rail line would be complete within a decade.

He did not immediately comment on Turnbull’s announcement as he was off sick on Thursday. But Victorian’s public transport minister, Jacinta Allan, said the government had committed to a rail link and would work with the federal government.

Turnbull said he was yet to speak with the premier but that he had sent him a “very detailed” letter. The letter suggested Victoria could use the $2bn it would get from selling its share of the Snowy Hydro Scheme. Significant private investment would also be needed.

“The goal would be to get the construction under way within a few years,” he said. “Obviously there is going to have to be a lot of planning. I wouldn’t want to, at this very early stage, estimate a time, but as soon as possible.”

The federal treasurer, Scott Morrison, said the railway would be one of national significance. He said a stronger economy meant the funds were available.

“This is a serious project,” he said. “Our money is on the table. It is in the budget and we are looking to form a real and new partnership with the Victorian government to make this happen. And equal partnership to see the project all the way through.”

