TT-Line is contacting those interstate who have booked travel on the Spirit of Tasmania vessels with caravans and motorhomes that they cannot self-isolate in them.
From Saturday, the state government imposed a requirement on visitors and Tasmanians returning from the mainland to self-quaratine for 14 days.
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Infrastructure Minister Michael Ferguson said on Wednesday people would not be able to self-quarantine in caravans and motorhomes.
He said anyone who had their booking cancelled as a result of government restrictions would have their ticket price refunded.
Premier Peter Gutwein said earlier in the day that only essential travellers and Tasmanians returning home would be allowed to travel on the Spirit vessels.
"As from today, if you are travelling and it's non-essential travel, do not come," he said.
"Do not get on the TT-Line. What we will do is turn you around and ask you to go back."