State-owned ferry firm Caledonian MacBrayne has paid more than £300,000 to customers affected by cancelled sailings.
Highlands and Islands MSP David Stewart obtained the figures – which cover the last three years – from the Scottish Government.
Transport Minister Derek Mackay told him that since July 2012 the total paid out was £305,758.
Serco, which now runs the services to Orkney and Shetland, paid out just £6,485.
Mr Stewart said the situation should be monitored “very closely”.
The MSP said: “This is clearly an immense some of money that has been paid out by Cal Mac in the form of passenger compensation.
“This is due to the EU regulations that are in place that protect passengers who are booked on services that are delayed or late.
“I think it is necessary though to delve deeper into these figures to understand exactly what compensation has been paid out and for what reasons.
“I intend to lodge further questions to the minister asking for a breakdown of the compensation figures.
“I am seeking further answers over this huge level of compensation and will be meeting the managing director of Cal Mac in the near future and hope to discuss this issue with him at greater length.”
A spokesman for Caledonian MacBrayne said the company carried 4.6 million passengers every year on 130,000 sailings over 49 routes.
“The technical reliability is also 99.9% and the compensation should be seen in the overall context of the volume of passengers and sailings,” he said.
European legislation was changed three years ago to allow people to reclaim money for sailings cancelled by technical issues.
The scheme does not allow claims for weather-related delays or for freight.
The EU Passenger Rights Regulation initially covered airlines but was extended in 2012 to cover ferries.