A second union, the TSSA, has voted for strike action in the row over the future of ferry services.
Its 100 members have voted by 55.6% to walkout in protest against the tendering of the Clyde and Hebrides ferry contract.
A threatened second strike by the RMT was suspended after Ministers agreed to delay the tendering process to allow peace talks to take place over the dispute.
TSSA leader Manuel Cortes said it was now time for Ministers to scrap their tendering policy.
“Both the people who work on the ferries and the communities they serve have made their feelings quite clear on this issue. They want this vital service kept in public hands.
“Ministers should start listening to the people they are meant to represent and stop blaming Brussels for this ham fisted decision.”