Islanders are being held to ransom in the first shipping strike since 1966, Shetland MSP Tavish Scott has claimed.
Northern Isles ferry staff started their first 24-hour strike yesterday.
RMT union members on Orkney and Shetland routes voted for action on various dates up to 30 December.
They claim Serco Northlink Ferries wants to cut jobs. The operator said it is not planning any compulsory redundancies and will make every effort to maintain the lifeline services.
Scottish transport minister Keith Brown expressed disappointment at the strike.
Sunday’s Aberdeen/Orkney/Shetland sailings also face action, from 8am until the same time on Monday. The union said its members were “prepared to fight for their future livelihoods”.
But Mr Scott said: “The Scottish Government must force the union and the employer to sort this out and stop any more disruption to the Northern Isles’ lifeline ferry services.”
He added: “Shetland hasn’t faced this situation since 1966. Islanders are fed up of being held to ransom and I expect those responsible – the union, government and employer – to get this sorted out.”