Ferguson Marine Engineering says one of the vessels being built for CalMac will not be ready until 2024.
The Scottish Conservatives described the latest delay as "beyond shambolic".
Ferguson obtained a 424-page document from a design consultant setting out CalMac's technical requirements, while other bidders had to rely on a more limited 125-page specification. A key section of its bid was mostly cut-and-pasted from this longer document The Port Glasgow shipyard fell into administration in August 2014, but was bought a week before the independence referendum by Jim McColl, a businessman who sat on First Minister Alex Salmond's council of economic advisers.
But the project has been beset by problems and the yard has been nationalised after going back into administration.The delays have added to pressure on CalMac's old and increasingly unreliable fleet.
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