Ms Sturgeon is known for tightly controlling her ministers and The Telegraph understands that she, or John Swinney, the  then finance secretary, would usually sign off on all major decisions at the time.

‘Absolutely laughable’ for Sturgeon to deny blame

Douglas Ross, the leader of the Scottish Tories, said it was “absolutely laughable” for Ms Sturgeon to “attempt to pin all the blame” on Mr Mackay for the ferries fiasco, increasingly being seen as one of the worst public procurement scandals in the history of devolution.

Mr Mackay, once seen as a likely successor to Ms Sturgeon, resigned in February 2020 after it emerged that he had bombarded a 16-year-old school boy with inappropriate social media messages.

“At the time he was a junior level minister,” Mr Ross said. “This would have gone far higher up the chain, indeed, I’m certain it would have gone straight to the First Minister.

“So I absolutely would want to see Derek Mackay appearing in front of any committee looking into this, but also the First Minister because they all have got crucial questions to answer.”

In a scathing report this week, Audit Scotland said there was a lack of written evidence to explain why SNP ministers approved the deal even after the Port Glasgow yard, then owned by businessman Jim McColl, reneged on a funding guarantee designed to protect taxpayers.

CMAL, the government agency which owns Scotland’s ferries, urged ministers to axe the deal but their concerns were rejected.

Mr McColl, one of the most prominent business figures to back independence, had saved Ferguson Marine in the weeks before the 2014 referendum in what was seen at the time as a coup for the Yes campaign.

The ferries contract was awarded to his yard the following year, despite its bid being the most expensive.