The union said Estonian seafarers on the7,600-gt Clipper Ranger (built 1995) running between Ullapool and Stornoway are working for as little as£4.19 ($7.10) per hour.
State-run CalMac has agreed to make thepayment to bring the wages up to the RMT rate for ratings on the Clyde andHebrides network.
But Seatruck has not accepted the offer.
The RMT said jobs would be at threat if thepolicy were allowed to continue.
Seatruck
