The RMT union has called for a meeting with the Government after it emerged that P&O is replacing Portuguese ratings on the Pride of York and Pride of Hull ferries with Filipino crew, working on tours lasting for up to six months.
Last year Hull MP Karl Turner raised concerns in the House of Commons over "slave labour" rates, saying Lithuanian cooks on the Pride of York were being paid under £2 an hour and Filipino able-bodied seafarers on the Pride of Hull the equivalent of £3.40 an hour. P&O has routes from Hull to Zeebrugge and Rotterdam.
At the time Small Business Minister Kelly Tolhurst said it was "unacceptable" and said she would be prepared to meet the MP.
A meeting has not yet taken place with either Mr Turner or the union, according to the RMT.
The RMT said crews working as "OBS" ratings, whose roles include waiter, chef and steward, are paid below the national minimum wage to work two-month tours of duty, with no pension provision.
The Filipino seafarers would be on the same conditions, but contractually obliged to work for tours lasting up to six months, which the RMT claims raises safety as well as employment concerns.
RMT general secretary Mick Cash said: “It is frankly appalling that just over a month since the Tories won the General Election promising to help northern cities like Hull that they are sitting on their hands while a major local employer smashes apart working conditions and denies local people the opportunity to take up decent jobs in the shipping sector."
However, P&O said the RMT was "being dishonest and trying to politicise a simple crewing change that is not affecting terms and conditions".
The company said most of their foreign workforce lived on board throughout their tour of duty and the rates paid were “fair” compared to wages in their home countries.
A statement said: "We comply fully with International Transport Federation agreements, which we have voluntarily put in place on our North Sea ships.
"The rates of pay are negotiated through the International Transport Federation.
“We are one of the largest single employers of UK seafarers and also have many agency colleagues from other countries working for us.
"The majority have no interaction with the British economy as they live on board on an 'all found' basis during their tour of duty and are employed at fair rates of pay when compared to wage levels in their home countries.
"Return flights to their home countries are included in their contracts, as required by the Maritime Labour Convention, and they benefit from food and accommodation free of charge.
"This is in line with the crewing practices of other shipping companies.”
The Department for Business, Energy and Industrial Strategy has been approached for a comment.