Former Scottish Government minister Derek Mackay says he takes his share of responsibility for the failure to deliver two ferries for CalMac's west coast routes.
He was speaking to Holyrood's Public Audit Committee, which is looking at why the vessels are years late and over-budget.
He denied that the contract was awarded to Port Glasgow-based Ferguson shipyard for political reasons.
Mr Mackay resigned in 2020 amid a scandal over messages to a teenage boy.
Holyrood is holding an inquiry into delays and overspends at Ferguson Marine, which is still building the two ferries.
The Glen Sannox and as-yet-unnamed 802 will be at least five years late when they finally come into service.
Costs have risen hugely from £97million to £250million.
Questions over contract
The BBC reports that there are questions over why the contract was awarded to Ferguson Marine despite concerns over its suitability.
These were raised by CMAL (Caledonian Maritime Assets Limited), which buys ferries for ferry operator CalMac. Both organisations are owned by the Scottish Government.
Mr Mackay had not been seen in the Scottish Parliament since he stood down as finance secretary and resigned from the SNP more than two years ago. He finally left Holyrood at last year's election.
He told the committee: "I recognise the catastrophic failure at Ferguson's to complete the vessels on time and on budget. That is deeply regrettable.
"What I don't regret is protecting the workforce."
The former transport minister said he did not think there was a political agenda, or that the decision was rushed at all.
There was a "methodical approach" to procurement, he said.
Best of intentions
"I recognise the failure of it, but it was made with the best of intentions," he said. The decision was about "getting the vessels built in Scotland and ensuring the future of the yard", added Mr Mackay.
He told the committee that ministers "don't ordinarily sign contracts" and it would have been officials from CMAL - who led the procurement process - who physically signed off the contract.
Earlier this year, an Audit Scotland report highlighted how the deal was approved by ministers in 2015 without the normal financial safeguards being in place.
Committee convener Richard Leonard later said the hearing brought clarity to some central issues, but there were still major differences in the versions of events stretching back to February 2015.
He said: "We have today decided to invite the first minister to give evidence at a future meeting to help us get to the bottom of what has gone badly wrong with the delivery of ferries 801 and 802 for the Clyde and Hebrides.
"We will also consider any further next steps necessary to be able to report to parliament on our findings."
Sweeping changes at CalMac
Meanwhile, Transport Minister Jenny Gilruth has announced plans for sweeping changes to the way CalMac ferries is owned and operated.
She told MSPs she plans to consult on changes to the west coast ferry service.
The BBC says it follows major disruption in recent months, caused by breakdowns and a lack of ferries.
The minister told the Scottish Parliament "things have got to improve for our island communities".