All of the services, except Gourock to Dunoon, will be up for grabs next year when a new contract will start.

The Scottish Government recently announced that the selection process for the operator is now under way.

CalMac currently run Wemyss Bay to Rothesay, Largs to Cumbrae and Ardrossan to Arran under the Clyde and Hebrides Ferry Services (CHFS) contract.

It is being re-tendered and will run for eight years from October 2016.

Gourock to Dunoon is operated by CalMac subsidiary, Argyll Ferries, and will be re-tendered from 2017.

Labour's Katy Clark said the re-tendering of the services raises the prospect of them being potentially transferred from the public to the private sector.

A shortlist of bidders will be asked to submit tenders in June, with the successful bidder likely to be announced in May next year.

She said “The STUC and CalMac trade unions have convincingly highlighted that there is no need for the Scottish Government to press ahead with this expensive and disruptive process, but Scottish ministers have refused to listen.

“The Scottish Government’s track record on protecting our ferry services does not inspire confidence.” Transport minister Derek Mackay says the government has made a clear commitment to ensuring safe and reliable services for ferry users.

He stressed that all of the CHFS services will be tendered as a single contract.

Mr Mackay added: “We are now focused on ensuring a fair and open competition that leads to getting the very best deal for all of the communities of the Clyde and Hebrides.”