Twenty-one Dutch seafarers are threatened with redundancy, following the sale of Netherlands flagged tankers Alcedo, Ardea and Dutch Faith.
Nautilus International industrial officer Bert Klein said the tanker operator was operating a social dumping strategy by importing cheap labour from overseas to replace existing Dutch crew.
'We demand that Essberger retains our members instead of pushing for redundancy,' he said.
'The usefulness and necessity of this ill-advised plan are still completely unclear to us. Esberger management refuses to share necessary information with us to be able to form a well-founded opinion about it.'
Essberger recently established a partnership with Stolt Tankers, resulting in a joint venture E&S Tankers. The E&S fleet consists of 45 ships.
Separately, Essberger invested in eight new tankers, the first of which will be flagged in Madeira. No additional information is available for the remaining vessels.
The number of Essberger ships under the Netherlands flag has fallen from 11 to eight.
Nautilus International is very concerned about the trend to flag out from the Netherlands. 'We have seen this with Maersk and apparently Essberger is following its bad example. But just like at Maersk, we are on top of it, together with our members!'
Nautilus does not rule out industrial action at Essberger if the employer does not return to the negotiating table.