Roy Brannen, the former Chief Executive of Transport Scotland, also told MSPs John Swinney and Nicola Sturgeon had no role in approving the controversial decision to award the Ferguson Marine ferries contract.
The SNP have been under continued pressure after an Audit Scotland investigation found the contract for two delayed and overbudget CalMac ferries was approved by ministers without normal financial safeguards. The ships, still being built at the Port Glasgow yard, will be five years late and could cost more than £250m.
The ships will not be ready to go to sea until 2023, while total costs have increased by up to £12m - on top of the £240m estimate given by Audit Scotland previously.
Mr Brannen, the now Interim Director-General Net Zero, told a Scottish Parliament Committee the decision to approve the contract was made in full by former transport minister Derek Mackay.
Speaking about ministerial approval for the contract at the Public Audit committee on Thursday, Mr Brannen said: “If it’s a transport project then that would be the minister of transport – it’s entirely within their portfolio.
"If it’s a wider issue such as bringing ScotRail into public ownership then that might be something that’s considered much wider than a single minister as it has a wider Scotland approach.
"Given all we were procuring at that time and bearing in mind we had around £2 to £3 billion worth of work underway with Queensferry Crossing, the M8, 73, 74, Aberdeen Western Peripheral, the ferries contract would have been entirely the decision for the minister for transport. ”
Mr Brannen also said the First Minister was not involved in the decision, adding: “The First Minister said at parliament they have collective responsibility for all decisions and that’s correct.”
The Interim Director-General Net Zero said it was “regrettable” the Scottish Government could not identify the paper trail exchange but added “it did turn up”.
Earlier this month, Scottish Conservative leader Douglas Ross said the Scottish Government waited for the Deputy First Minister John Swinney to give the “green light” over the deal.
Civil service advice in an email chain revealed the Deputy First Minister had sight of the deal.
He added: “Honest John's hands are all over this dodgy deal".
However, asked if the Cabinet secretary of finance, then John Swinney, had a role in the decision taken, Mr Brannen said: “No, so the cabinet secretary for finance would agree the budget which he did.
"He doesn’t have a role in the decision to sign off awarding CMAL with the contract – that rested with the minister of transport at the time.”
The continued pressure on the Government over ferries comes as Nicola Sturgeon is to miss First Minister’s Questions as she continues to recover from Covid-19.
Deputy First Minister John Swinney will stand in for Ms Sturgeon on Thursday, taking questions from opposition leaders and MSPs.
Mr Swinney’s turn at First Minister’s Questions may have come at an inopportune time for the Scottish Government, with opposition MSPs continuing to question his involvement in the sign off of a contract for the two late and over-budget ferries.