Some workers at shipbuilder Cammell Laird have voted to strike over fears 290 jobs could be axed despite the yard securing two big Royal Navy contracts.
Last month it was announced that the Merseyside base would receive £620m to support Royal Fleet Auxiliary tankers.
The Unite union said about 40% of jobs could still be lost by March. Nearly 80% backed strike action in a ballot in which three-quarters of members voted.
A Cammell Laird spokesman said it would continue to hold talks with the union.
He explained the firm "can have peaks in demand for skilled and semi-skilled labour, which is the nature of contract-based industries".
"However, as a result of numerous contracts entering the latter phases, and without certainty in the award of similar contracts in the immediate term, the company needs to address its cost base to remain competitive.
"We continue to bid for numerous contracts around the world and we remain very optimistic for future growth."
Unite regional officer Ross Quinn said: "Cammell Laird bosses need to wake up to the resolve of the workforce to take a stand against these unnecessary job cuts and turn the tide against casualisation."
He said Cammell Laird had agreed to look at a union proposal "proving they can avoid dismissing anyone until February".
"However, should bosses press ahead and sacrifice the livelihoods of our members for their own cost-cutting ends, then there is the real prospect of them provoking industrial action and putting future contracts at risk."
Albie McGuigan, regional organiser for the trade union GMB, said: "This proposed redundancy of 291 highly skilled workers and support staff is a deliberate attempt to restructure through redundancy and place the future of a loyal workforce in peril.
"If this decision is not reversed it will lead to untold hardship on the redundant workers and their families."
Shipyard workers recently built the £200m vessel RRS Sir David Attenborough, which includes a yellow submarine named Boaty McBoatface after an online campaign.