A crowd of about 200 people rallying behind striking oil tanker crew members has marched on a senator's office in north-west Tasmania.

The crowd gathered in Devonport to show their support for 36 Australian crew members of the Alexander Spirit, who were told last week they would be replaced by foreign workers on a new international route.

Since Friday, the crew has been refusing to set sail for Singapore until they receive more information about their redundancy entitlements.

ACTU president Ged Kearney led a rally through the streets, joined by Senator Jacqui Lambie, Opposition Leader Bryan Green, Alexander Spirit crewmen, union members such as Spirit of Tasmania workers and members of the public.

"Do we want to see migrant workers in our shores be exploited, be paid $2 a day, be subjected to conditions that nobody would stand for in this country?" she asked the crowd.

Calling on the Federal Government to intervene, the marchers descended on the office of Liberal senator Richard Colbeck before proceeding through Rooke Street Mall.

Senator Lambie questioned the influence of political donations by Caltex to the Coalition.

"The Coalition could come and put some heat on Caltex and make sure that these jobs remain," she said.

"That can be done but I haven't seen anything.

"In fact, if anything, the Coalition is on the run and they're running in the opposite direction."

Federal Employment Minister Eric Abetz rejected the suggestion, saying he shared concerns about the loss of jobs.

Crew member Andy Poynter from Newcastle said he had worked on the ship for four years.

He said the ship's owner Teekay Shipping was keeping the workers in the dark.

"We're willing to stay here [in Devonport] until we get answers to our questions," he said.

"Where is the ship going to trade after this? What [are] the plans for it? They can't tell us none of that."

Mr Poynter said the crewmen had been given no further details about their redundancies.

"We want to get that all-clear before we sail," he said.

Teekay is seeking an order from the Fair Work Commission in Sydney to stop the industrial action.

The hearing has been adjourned until Tuesday afternoon.