Eilidh Mactaggart left her role as chief executive of the Scottish National Investment Bank (SNIB) abruptly on Friday, with no reason given.
When questioned on Tuesday about the move, Ms Forbes refused to say why as she sought to reassure MSPs that Ms Mactaggart’s successor would be agreed by ministers.
“I recognise that there is significant interest and questions around the chief executive’s resignation due to the seniority of her role and the importance of the SNIB to Scotland’s economy,” Ms Forbes said in response to a question by Scottish Tory finance spokeswoman Liz Smith.
“The reasons for the former chief executive’s resignation are a matter for her and the bank’s board.
“The board have kept ministers up to date with all matters relating to the chief executive and the executive team and board members will continue to provide strong leadership and direction for staff and bank clients.”
Pushed on the issue by Ms Smith – who asked if the Finance Secretary understood the need for “full transparency” given the significant public investment in the bank – Ms Forbes again refused to answer.
“I would echo the comments that Liz Smith has just quoted me on because since its launch, the bank has made significantly good progress,” she said.
The Finance Secretary added: “As I said already, I know there is public interest, there is political interest in answers and ensuring that there is transparency.
“I can say, once again, matters related to the former chief executive’s resignation from the bank are very much for the former chief executive and for the bank’s board.”
Ms Mactaggart, 47, took up the role as the bank's chief executive following spells as managing director for MetLife Investment Management and as a director of the Commonwealth Bank of Australia. The Glasgow-born banker said at the time: "The establishment of the Scottish National Investment Bank will provide longterm patient capital support for ambitious companies, the third sector and infrastructure projects, underpinned by the transition to net-zero carbon emissions.