Shipping union RMT is tomorrow set to step up its campaign against companies that exploit foreign workers as it targets a south coast ferry firm.
Members will hand out leaflets in Portsmouth city centre at 3pm and protest against Condor Ferries at the city's freight and passenger terminals.
RMT claims Condor employs Ukrainian workers on £2.35 an hour - just £28 for an 12-hour shift - to work three months on, one month off unpaid on routes between Portsmouth, Weymouth or Poole and the Channel Islands.
Britain's minimum wage is £6.19 per hour for workers older than 21.
Unions call the practice "social dumping," where workers from abroad are paid peanuts and treated badly and used to drive down locals' pay and conditions.
RMT has repeatedly warned that the government's "light touch" regulations in the Equality Act leave seafarers vulnerable to exploitation.
General secretary Bob Crow said: "The modern-day slavery on our ships of shame is now starting to grab media attention.
"The super-exploitation of foreign nationals in the British shipping industry is a massive scandal that the political elite want to keep quiet.
"Social dumping is a mechanism seized on by some of the most rotten employers in the book to try and batter down wages and conditions."
Condor did not respond to the requests for comment.