Professor Jason Leitch is coming under pressure to stand down as Scotland's National Clinical Director for mocking opposition politicians in private WhatsApp messages.

In the chat with Humza Yousaf, published by the UK Covid Inquiry on Friday morning, the civil servant accused a Conservative MSP of being “rude” and "harrumphing like a child" and described a Labour MSP as a "smartarse".

Labour leader Anas Sarwar said the official had shown “extremely unprofessional behaviour” and said it was proof that the “rotten culture” of Scotland’s political leadership had permeated into the senior civil service.

The Scottish Conservatives described the official as a “cheerleader” for the SNP and called for him to “do the decent thing and resign or be sacked as national clinical director.”

READ MORE: Labour calls for Jason Leitch to be sacked as Clinical Director

The messages were sent just four weeks after the 2021 election when Professor Leitch was briefing MSPs on the state of the pandemic.

He told Mr Yousaf: "Just done MSP briefing. They were mostly fine. Very reasonable and predictable. [Tory MSP] Edward Mountain rude and [Labour MSP] Daniel Johnson a smartarse. Otherwise fine.”

When Mr Yousaf asked for more details, Prof Leitch replied: “My Mum taught me never to be rude. Mountain was head shaking and a child.”

The First Minister replied to say Paul Sweeney, another Labour MSP, “will also be one to watch, he will tell you how to do your job”.

Prof Leitch then claimed that Labour leader Anas Sarwar had told him that he was "struggling" with Mr Sweeney and with "new girl Mercedes" [Villalba, a Labour MSP].

The Herald:

Responding to the messages, Mr Mountain told The Herald: “My job wasn’t to be subservient to the Scottish Government – it was to represent the views and concerns of my constituents.

“Ministers and officials should have spent less time worrying about their sensitivities and more time working to tackle the virus.

“These petulant interchanges reflect very poorly on Jason Leitch and the First Minister.”

Taking to Twitter Mr Johnson said he had only asked Prof Leitch why the Scottish Government was allowing fan zones to go ahead for the football, but was prohibiting nursery graduations.

"If that makes you a smart arse so be it!" he added.

READ MORE: Jason Leitch confirms he wiped pandemic WhatsApp messages

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 now First Minister responds: “I am winging it! And will get found out sooner rather than later.”

Mr Sarwar was asked about Prof Leitch’s comments and particularly if he felt betrayed by the clinician for sharing a private conversation with Mr Yousaf.

“I don't really care,” he told LBC. “I care more about the betrayal of the Scottish people.”

He defended his comments about Mr Sweeney and Ms Villalba saying it had been difficult to mix as a group following the 2021 vote because of the social distancing required by the pandemic.

“For the National Clinical Director to be briefing newly elected MSPs and then after briefing those newly elected MSPs to start ranting about them, in that way, I think shows an extremely unprofessional behaviour,” he said.

“And again shows I think, the pettiness of yes our political leadership in this country, but how that permeated then in terms of that rotten culture to the more senior civil service.”

Scottish Tory chair, Craig Hoy said: “It is no wonder that he became a cheerleader for the industrial-scale deletion of WhatsApps from those at the top of the SNP-Government, and that it became a ‘pre-bed ritual’ for him and his colleagues to hide petty attacks – and much else besides – such as these.

“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.”

The messages could be a breach of the civil service code, particularly the rules around political impartiality, which says officials must "act in a way which deserves and retains the confidence of Ministers, while at the same time ensuring that you will be able to establish the same relationship with those whom you may be required to serve in some future Government."

Meanwhile, the Scottish Tories have also urged Presiding Officer Alison Johnstone to reconvene Holyrood’s Covid-19 Committee.