A leading Scottish Government adviser branded a Conservative politician “rude” and a Labour MSP a “smart arse” after giving a coronavirus briefing, messages published by the UK Covid-19 Inquiry reveal.

National clinical director Professor Jason Leitch made the remarks in an exchange with First Minister Humza Yousaf, who at the time was Scotland’s health secretary.

Papers released by the inquiry show a conversation between the two men on WhatsApp on June 11 2021, with Prof Leitch telling Mr Yousaf he had just led a briefing for MSPs.

While he said the MSPs were “mostly fine” and “very reasonable and predictable”, Prof Leitch added: “Edward Mountain rude and Daniel Johnson a smart arse.

“My mum taught me never to be rude. Mountain was head shaking and harrumphing… like a child.”

Mr Yousaf replied: “Doesn’t surprise me about Mountain or DJ frankly.”

He then advises Prof Leitch that Labour MSP Paul Sweeney would “be one to watch”, with Mr Yousaf saying: “He will tell you how to do your job.”

I am winging it! And will get found out sooner rather than later

Prof Leitch responds by saying Scottish Labour leader Anas Sarwar “says he’s struggling with him” and another of his MSPs, Mercedes Villalba – who the adviser describes as a “new girl” after she was elected to Holyrood that month.

In the messages, Mr Yousaf, who became health secretary in May 2021 after the Holyrood election, also tells Prof Leitch he is “winging it” in the post.

Mr Yousaf remarked that the pandemic meant “everyone is of course a public health expert”, with Prof Leitch telling him: “You actually are. Three weeks training!”

The minister responds: “I am winging it! And will get found out sooner rather than later.”

In an earlier exchange between the two men, dated May 20 2021, Prof Leitch complained that he can “barely understand” Scotland’s Chief Medical Officer, Professor Sir Gregor Smith.

He made the remark after Mr Yousaf asked to be kept informed about what media appearances the adviser was doing.

Mr Yousaf said: “Not for permission no, but helpful to know what bids youre doing so i can catch up as I often plagiarise what you are saying – verbatim… just to make it look like i know what I’m actually talking about.”

Prof Leith said he will “definitely” tell him, and when Mr Yousaf added: “Expect some more requests for layman explanations,” the adviser replied: “Easy. It’s my only skill.”

He then adds: “And I barely understand Gregor either but the boffins like him.”

The UK Covid-19 Inquiry has already heard from both Mr Yousaf and Prof Leitch as it takes evidence during a series of sessions in Edinburgh.

These will continue next week, with Jeane Freeman, who preceded Mr Yousaf as health secretary, and former first minister Nicola Sturgeon both due to answer questions.

It would be inappropriate to comment on the detail of evidence being considered by the UK Covid Inquiry while hearings are ongoing

Scottish Conservative chairman Craig Hoy said: “It is totally inappropriate that a supposedly impartial health adviser was behaving like a paid-up member of the SNP during the pandemic.

“The messages that have come to light from others reveal that Jason Leitch laughed as the future first minister insulted others, and that he even joined in the mudslinging at politicians from other parties.”

He added: “Mr Leitch must now do the decent thing and resign or be sacked as national clinical director, as it’s clear that he’s not fit for the role.”

A Scottish Government spokesperson said: “The Scottish Government is committed to responding to both the UK and Scottish Covid-19 inquiries, as learning lessons from the pandemic is vital to prepare for the future.

“It would be inappropriate to comment on the detail of evidence being considered by the UK Covid Inquiry while hearings are ongoing.”