The two ships, hull 801 and 802, are now more than three times over budget with the latter now set to be delivered in 2024, six years late.
A BBC documentary this week alleged that the procurement process for the two vessels had been “rigged”, partly due to Ferguson Marine being considered despite being unable to offer a full builder’s refund guarantee.
This guarantee was a mandatory minimum requirement and without it, the financial risk to the taxpayer in the event of overspends or delays increased.
The shipyard’s owner, Jim McColl, claims the ferry procurement body CMAL was always aware of Ferguson’s inability to provide a full refund guarantee, with CMAL claiming it was only told after the yard was named preferred bidder in August 2015.
During Mr McColl’s evidence to the Public Audit Committee, he said SNP MSP, Stuart McMillan, had approach the then-transport minster Derek Mackay to ask about builder’s refund guarantees.
The letter from Mr Mackay to the MSP, who represents the constituency of Greenock and Inverclyde where Ferguson’s is based, was sent during the early stage of the procurement process and raises questions about the potential of political influence around the bid.
In it, Mr Mackay outlines to his SNP colleague that the ferry procurement body CMAL has previously taken an “alternative approach” to the requirement for a builder’s refund guarantee.
CMAL went on to accept the contract with Ferguson’s without a full builder’s refund after getting significant financial assurances and commitments from Transport Scotland.
Mr McMillan has been asked to hand over all correspondence he sent to and received from the Scottish Government around the procurement process.
Keith Brown, deputy SNP leader and then-infrastructure secretary and Mr Mackay’s boss, has also been asked to provide evidence to the committee on his role in the procurement process and the decision to agree the contract.
The Public Audit Committee is also to hear evidence from Nicola Sturgeon on the ferries saga later this year.