About a third of the workforce from Appledore Shipbuilders in north Devon have been transferred down to Babcock's sister yard at Devonport, Plymouth.
The yard near Bideford has finished some major packages of work on Britain's new aircraft carriers.
Large parts of the yard are currently standing idle for lack of new orders.
Heathcliffe Pettifer, regional union officer with Unite said: "The likelihood is regardless of the arrangements around work, if an order was announced tomorrow we're still looking at a blip which means that more than 100 people are likely to be transferred by the end of March."
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Mr Pettifer said workers were finding digs in Devonport and were not sure of their rates of pay.
"This is all against a backdrop of potential voluntary redundancies," he said.
A statement from Babcock said: "Our priority is to offer our employees at Appledore who wish to continue to work with Babcock a way to do so and have provided opportunities on our other sites in the expected workload dip.
"We remain focused in our efforts to successfully secure future work for the yard."
Conservative MP Geoffrey Cox said: "Appledore and Babcock are making enormous efforts with the assistance of the government to find alternative work streams."
The last main vessel being built at Appledore, for the Irish Navy, is due to float out later this year.
A shipyard which builds navy vessels has seen 70 workers transferred to another site because of a shortage of work, unions say.