About 30 people protested outside the Isle of Man parliament over concerns about a threat to ferry services.
Union officials joined workers from the Steam Packet Company to highlight fears of cuts to jobs and services after the company lost major freight contracts.
MHKs and MLCs were lobbied by placard-carrying protesters as they arrived for the November sitting of Tynwald.
The company said it was reviewing its operations following the launch of a rival freight service last month.
Protesters are urging the government to come up with a contingency plan in the event of the Steam Packet Company cutting back services.
Chris Bowen, of the Nautilus union, said: "As unions we are very concerned for our jobs because if it keeps going the way it is, there is going to be a reduction in services.
"And if there is a reduction in services there will be a reduction in jobs as well."
The Ramsey-based Mezeron's daily freight service between Douglas and Liverpool is a direct competitor for the Steam Packet, which employs about 300 people on the island.
Steam Packet passenger services, which are subsidised through its freight division, are currently being re-examined.
Chief executive Mark Woodward has said that any substantial reduction in freight income will have an impact on passenger services.