A trade union will demonstrate at Holyrood this week as the final decision on who will operate west coast ferry routes looms.
Members of the RMT will gather outside the Scottish Parliament on Thursday to lobby politicians as they get ready to rule on whether CalMac will retain the routes or they will be given to Serco.
The contract is due to be awarded by the end of the month.
RMT general secretary, Mick Cash, said: “Our members and their supporters are encouraged to attend what will be a positive demonstration of support for CalMac and the retention of publicly-operated lifeline ferry services.
“We want to put all MSPs on the spot as to whether they support the CalMac bid or the Serco bid for the next Clyde and Hebrides ferry services contract and the union will use those replies to put further pressure on the Scottish Government to award this contract to CalMac.
“The Scottish Government have a simple choice when it comes to the lifeline ferry routes – they either back their own staff who run the lines as a public service in the public interest or they back the profit-driven Serco brand.
“This is a massive decision that will set the tone right at the start for this new SNP administration and RMT will continue to jack-up the pressure for Scotland’s public services to be run for the public benefit.”
A Transport Scotland spokesman said: “The final stages of the tender process are still to be concluded by Transport Scotland, with the outcome expected to be announced by the end of May.
“This provides the necessary period of time to ensure all arrangements are in place for the new contract to start on October 1, 2016.
“The Scottish Government fully recognises that Scotland’s ferry services provide economic benefits for our island communities.
“We are fully committed to the continued delivery of safe, reliable, publicly-owned ferry services, as evidenced by the record £1billion investment in these services, vessels and ports since 2007.”