The Rail, Maritime and Transport (RMT) union has planned a protest outside a Glasgow recruitment office which was reportedly involved in hiring staff to replace sacked union members on P&O's ferry routes.
Union's general secretary Mick Lynch said the demonstration will take place at the offices of Clyde Marine Recruitment, Govan Road, on Monday from 11am.
On Saturday, the union's Scottish leader Gordon Martin hinted at the protest taking place when he addressed the Alba Party spring conference in Glasgow.