The Overland train service between Adelaide and Melbourne is likely to shut down at the end of the year for a lack of state government funding, Opposition Leader Peter Malinauskas says.
Journey Beyond Rail Expeditions, formerly Great Southern Rail, is not taking bookings for the service beyond December 31.
The state government cut its annual funding, worth $330,000, last November, but the Victorian government agreed to pick up the tab for 12 months.
Mr Malinauskas urged Premier Steven Marshall to step in and save the service.
"We know that, once these train services go, it is very hard to get them back," he said.
The Overland is the only remaining passenger rail service which stops at Murray Bridge, twice a week in each direction.
It has operated since 1887.