A protest continues onboard a oil carrier ship in Tasmania, with reports that stress and illness are delaying its departure.

The oil ship Alexander Spirit – which has been operated by Teekay Shipping for Caltex - has been docked in Devonport for 10 days, with its crew refusing to sail to Singapore on a trip they say will end with their sacking. 

The Maritime Union of Australia (MUA) met the ship's operator Teekay aboard the Caltex tanker over the weekend, and says that a number of crew members have now left the ship due to stress-related health problems.

“Mostly it's highly emotional, it's been the stressful situation they don't want, they said they just couldn't deal with it,” he told News Corp reporters.

It is now unclear whether there would be enough crew members on board to man the ship.

Mr Bray said counselling had been offered to the crew.

“The ship is an isolated workplace, they're away from support groups, they're away from family,” he said.

The crew's protest was last week ruled illegal by Fair Work Australia.

But Mr Bray said Teekay did not consider the crew to have breached the Fair Work ruling.

“They want to make sure firstly that they're creating a stable environment on board, and fair play to Teekay,” he said.

“The fact is they've realised the high level of stress on board and said we have to do something about that.”