Arran residents would pay more for a poorer ferry service if its mainland destination is moved, according to a community group.
Associated British Ports (ABP) this week announced it would invest £8m in its facility at Troon - but only if Transport Scotland moved the Arran service from its current base at Ardrossan.
It claimed the South Ayrshire town is already well-equipped to handle the next generation of CalMac ferries which will serve the route, while its sheltered harbour would improve reliability in adverse weather.
Arran Economic Group (AEG) said islanders would suffer if the plans went ahead.
It claimed there was no evidence the move would improve the reliability of the service, while costs would rise due to the application of the Road Equivalent Tariff.
Journey times would also go up as the route is not fully integrated with transport links, the group claimed.
AEC representatives have met transport minister Humza Yousaf to discuss the proposals and are now seeking to enter discussions with ABP.
A spokeswoman said: "Given the Scottish Government's track record of supporting and engaging island communities, putting their opinions and views to the forefront of all activity, the AEG members would ask that all parties recognise the current thinking and views of the Arran community and local representatives."
The proposals have also been met with dismay by North Ayrshire Council, with the facility at Ardrossan a vital job creator and income generator.
Council leader Joe Cullinane said the ferry terminal supports 165 jobs in the area, equating to £4.4m in wages, as well as drawing tourist spending.
He said: "The loss of the ferry port would be nothing short of cataclysmic for our area. We do, however, remain positive that common sense will prevail and that the Arran ferry will continue to run from Ardrossan for many, many more years to come."
Andrew Harston, ABP's director of short sea ports, said a move to Troon would result in a better service.
He said: "For the community on Arran, the connection to the mainland is absolutely vital and this should not be left to the mercy of the weather, as it has been for too long.
"The solution being offered by ABP at Troon, which is one of the most sheltered harbours on the west coast of Scotland, would represent nothing short of a transformation in the quality of the service on offer to the islanders and tourists."
Transport Scotland said no decision had been made about the future of the service.
A spokesman said: "We are committed to supporting our lifeline ferry services and providing the best possible service for the communities that rely on them. We are looking, in the first instance, at resolving the issues at Ardrossan harbour and have set up a ministerial task force to address this."
He added: "However, no options are off the table and we have received an approach from ABP about the potential use of Troon harbour for the Arran route. This was brought to the attention of the task force last month and was discussed by Mr Yousaf with Arran community representatives during his recent visit. To be clear, no decisions have been made and we will continue to engage closely through the taskforce and with all relevant stakeholders in analysing the various options for delivery of the Arran services as the process continues."