A shipping union will hold a protest at Aberdeen harbour over "poverty pay" on a freight ferry service.

Non-EU nationals working on Serco-run Northern Isles Seatruck Ferry Services are paid £3.66 an hour, according to the latest figures obtained by the RMT union.

RMT members will be at Aberdeen Harbour from 10.45am on Friday and will hold a demonstration by the Seatruck vessel.

The harbour protest will last until 11.15am and will then move on to Victoria Road in Torry, where there will be a demonstration outside the offices of Callum McCaig MP and Maureen Watt SNP MSP .

The protest will then move on to the bottom of Market Street next to the harbour, where leaflets will be handed out to the people of Aberdeen.

Mick Cash, RMT general secretary, said: "It is scandal that ships of shame are sailing out of Aberdeen, with workers on poverty rates that make a mockery of our legal minimum wage, under a contract that is under the control of the SNP administration.

"This outrage, which is stain on the reputation of the great city of Aberdeen, has to be ended and ended now. RMT is demanding urgent talks with the minister and an assurance that he will step in immediately to end this modern day slavery in Scottish waters."

A statement from Seatruck said: "The freight ferries Helliar and Hildasay have been operating successfully for many years on the lifeline service to the Northern Isles.

"The Seatruck Ferries vessels are on long-term charter to the concession holder Serco Northlink.

"Under the current legislation the national minimum wage is not applicable to the crew of these vessels."

It added: "The crew are not deemed to be 'ordinarily working in the UK' as they are working on a non-UK flagged vessel, are not UK residents, do not pay tax or NI in the UK and start and finish their tours of duty in their home countries.

"The vessels comply with all relevant legislation and operate a reliable high-quality service.

"Seatruck Ferries operates in a worldwide shipping market where NMW application in isolation would place the company at a serious disadvantage in relation to its competitors."