North Ayrshire Council’s Cabinet approved an agreement in June which triggered the beginning of the procurement process for the multi-million-pound redevelopment.

However, Transport Scotland said the tender design stage has identified that costs have risen significantly since the start of the project, and will need to be reassessed to take significant construction inflation and the expanded scope of the works into account.

The project plans now include technically challenging and costly berth realignment marine works to better accommodate new ferries, allow better vessel interoperability and ultimately improve service reliability and resilience.

Transport Scotland officials will now begin work to reassess project scope and costs for all funding partners involved.

Minister for transport Fiona Hyslop said: “I fully appreciate this will be disappointing news for the communities in Ardrossan, Arran and Campbeltown, and the frustration it will cause, but it is essential we reassess the cost of the project to ensure we deliver value for the public purse and funding partners.

“The decision to pause procurement has not been taken lightly, but it is essential we obtain an updated cost estimate and refreshed business case to support this project in light of significant changes to the original plans, which look to improve the resilience of the service and better accommodate new vessels that are due to enter service in the future.

“There will be no final decision on investment until the outcome of the business case review is reported to the Ardrossan Harbour Task Force, which is expected later this year.

“The Scottish Government remains committed to ensuring the Arran ferry service is fit for the future and we will continue to engage closely with the community throughout this process.”

Councillor Marie Burns, leader of North Ayrshire Council, said: “We accept that there are many challenges surrounding this project and while we are disappointed that there will be a further delay we acknowledge the decision to carry out a new business case.

“We remain absolutely committed to supporting and retaining the Arran ferry service from Ardrossan. We firmly believe that both the Arran and Ardrossan communities are best served by the provision of services from Ardrossan.

“We will make this case strongly during the business case review and remain confident a long-term plan can be established which will see ferry services to Arran remain and prosper in Ardrossan.”

James McSporran from Peel Ports Group added: “Like all the partners, we want to move ahead with this important development as quickly as possible. We’ll continue to work with Transport Scotland and North Ayrshire Council on the procurement of this complex and specialist engineering project.

“In the meantime, we can reassure the residents and businesses of Arran that the current terminal is very much fit for purpose and able to support their lifeline ferry service. We’ll continue to maintain it, as we always have done, to make sure this remains the case.”