An ex-Scottish Government official who told colleagues to delete WhatsApp messages so they couldn’t be made public has resigned from his current job after Nicola Sturgeon yesterday insisted he has "the utmost integrity and the utmost professionalism".

Ken Thomson, who was the Scottish Government’s director general for strategy and external affairs during the pandemic, has quit as chairman of the Institute of Chartered Accountants of Scotland’s (ICAS) regulatory board for “personal reasons”.

In evidence revealed by the UK Covid Inquiry, Mr Thomson advised his Scottish Government colleagues to delete messages and even boasted that “plausible deniability are my middle names”.

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In one message to deputy chief medical officer Lesley Steedman, Mr Thomson said: “Just to remind you (seriously), this is discoverable under FoI [freedom of information]. Know where the “clear chat” button is…”.

Mr Thomson also used the phrase “this information you requested is not held centrally”, a stock phrase the Scottish Government uses when refusing FoI requests.

Mr Thomson has denied the advice was an attempt to defeat requests for information and documents under FoI laws.

Ms Sturgeon was pressed over Mr Thomson’s messages during her mammoth evidence session in front of the inquiry yesterday, claiming the discussion was “light-hearted” and that she would read that as him reminding people to be professional on WhatsApp.

The former first minister heaped praise on Mr Thomson.

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She said: "Ken Thomson is somebody I’ve worked with throughout my time in the Scottish Government and he is a civil servant, as I say, of the utmost integrity and the utmost professionalism."

ICAS has now confirmed that Mr Thomson has quit the job, having only started with the organisation on January 1.

In a statement, ICAS said: “ICAS will shortly begin the process of appointing a chair of the regulation board.

“This follows Ken Thomson’s resignation as an ICAS public interest member of council and chair of the ICAS regulation board, for personal reasons.

“His resignation has been accepted with effect from 31 January 2024.”

The Edinburgh Reporter has suggested that ICAS has received angry complaints from grieving relatives.

One relative told the paper: “ICAS’s code of ethics claims that upholding high standards and promoting ethical leadership is at the heart of everything they do and quite frankly continuing with Mr Thompson as its regulatory chief is laughable.

Read more: Nicola Sturgeon admits deleting Covid WhatsApp messages

“I am glad ICAS has acted swiftly on this important issue but really they had little choice given the evidence which emerged at the Covid Inquiry.”

When Mr Thomson was appointed at the start of the month, ICAS CEO Bruce Cartwright said he was “a valuable addition to the regulation board and brings with him a wealth of experience”.

Mr Cartwright added: “Upholding high standards and promoting ethical leadership is at the heart of everything we do at ICAS.

“I know Ken will play an instrumental role in maintaining and enhancing our efforts.”

Mr Thomson held the position as director general for strategy and external affairs for the Scottish Government for 12 years, where he also oversaw Operation Unicorn, the Scottish ceremonies following the death of The Queen.