THE disgraced former SNP minister Derek Mackay has been formally requested to give evidence to MSPs about the CalMac ferries fiasco.

Holyrood’s public audit committee confirmed it had written to the former transport and islands minister about his decision to order the boats despite serious financial concerns.

The committee said it had initially asked for written answers in response to specific questions, and would decide its next steps after considering his answers.

He has already said he is willing to cooperate with the committee's inquiry into how the deal went so badly wrong.

In October 2015, Mr Mackay gave the green light to state-owned ferry owner Caledonian Maritime Assets Ltd (CMAL) to order two ferries from the Ferguson Marine shipyard on the Clyde.

The boats were meant to cost £97m and be delivered within three years, but are now £150m over budget and five years late, while the yard was nationalised after going broke.

CMAL had warned the Scottish Government at the outset that Ferguson's was unable to offer an industry standard refund guarantee that would have protected taxpayers in case of problems.

Labour committee convener Richard Leonard said MSPs had also asked a number of key players in the saga to give oral evidence.

These include CMAL chief executive Kevin Hobbs, former CMAL chair Erik Østergaard, and tycoon Jim McColl, the former director of Ferguson Marine.

Former Ferguson Marine chief executive officer Gerry Marshall has also been invited to attend a future evidence session.

In addition, two key civil servants have been asked to provide initial written evidence - former Transport Scotland chief executive David Middleton, who was in charge when the contract was agreed, and the former Director-General for Enterprise, Environment and Innovation in the Scottish Government, Graeme Dickson.

The deal between Ferguson’s and CMAL quickly turned sour, with rows over design changes, delays and money leading to the yard’s collapse and nationalisation in 2019.

Mr Mackay, who went on to become finance secretary, put much of the blame on Ferguson’s and its work practices.

He resigned from the cabinet in February 2020 after the Scottish Sun discovered he had been pestering a 16-year-old schoolboy with sleazy texts.

He then disappeared from Holyrood and public life, but earlier this year set up a one-man consultancy business called Lochan Associates Ltd.

He told the Sunday Times in April: “I am willing to co-operate with a parliamentary committee and do my best to answer any questions they may have.

"To do so as comprehensively as possible I will seek access to the necessary papers and information that I am entitled to as a former government minister.”

His evidence could prove extremely awkward for the Scottish Government.

First Minister Nicola Sturgeon has been accused of piling blame on Mr Mackay to spare deputy FM John Swinney embarrassment.

It emerged this month that Mr Swinney confirmed his “budget approval” for the ferries after Mr Mackay had backed the deal, and could in theory have vetoed it.

The Auditor General for Scotland has also said it remains unclear why ministers agreed to push ahead with the contract in spite of CMAL’s misgivings, as there is no written rationale.