Nicola Sturgeon described Boris Johnson as “a fucking clown” as he broadcast to the nation to announce a second Covid lockdown in October 2020, telling her chief of staff: “His utter incompetence in every sense is now offending me on behalf of politicians everywhere.”

The former first minister’s damning verdict on the UK government’s communications strategy – which she dismissed as “awful … we’re not perfect but we don’t get nearly enough credit for how much better than them we are” – was revealed during evidence at the UK Covid inquiry, which is sitting for a second week in Edinburgh.

Asked if the expletive-laden exchange on WhatsApp suggested that the relationship between Sturgeon and the former prime minister had broken down, her former adviser Liz Lloyd replied: “I think broken down to a degree overstates what was there to break.”

Evidence also emerged on Thursday morning of what appeared to be detailed decision-making on pandemic restrictions and strategy being conducted by WhatsApp messages, in seeming contradiction of Sturgeon’s insistence that she did not conduct her government’s Covid response through informal messaging.

Lloyd, who served as chief of staff and strategic adviser between 2015 and 2023 and described herself as Sturgeon’s “thought partner”, was shown several exchanges, including one regarding the numbers allowed to attend weddings and another suggesting “a good old-fashioned rammy [quarrel]” with the UK government over furlough policy.

Usman Tariq, junior counsel for the inquiry, noted that Lloyd’s messages “were the first provided by anyone involved in the Scottish government’s response to the pandemic to this inquiry”.

Asked how the public would have been able “to understand how and why this decision was made” if Lloyd had deleted the messages, she responded: “They might not see the reflection but they would know the advice.”

Lloyd’s evidence follows a succession of revelations about how senior ministers and officials deleted informal messages and exhibited apparent disdain for freedom of information rules.

There was a furious response last week when the inquiry heard that Sturgeon “retained no messages whatsoever”, while the national clinical director, Jason Leith, joked in a group chat that WhatsApp deletion was his “pre-bed ritual”.

Sturgeon has since clarified that the inquiry does have messages relating to the pandemic, although they were not retained on her device, and insisted: “To be clear, I conducted the Covid response through formal processes from my office in St Andrews House, not through WhatsApp or any other informal messaging platform.”

Asked why Sturgeon deleted messages but she did not, Lloyd suggested that in the exchanges “I am the official so she may have had reason to think Liz is taking care of it”.

She said anything salient was put on the official government record and she was “not familiar” with the policy referred to by other Scottish officials that informal messages should be regularly deleted.

Lloyd was also questioned about an exchange with Sturgeon in which Lloyd wrote: “I think I just want a good old-fashioned rammy [with the UK government on extending furlough to Scotland in November 2020]. She described this as “an expression of frustration that we were not able to manage the pandemic at this point in time in the way we wanted”.

She said: “There were a lot of things in Covid the UK government did or didn’t do and we just let it go. I felt the issue of furlough was materially important to the handling of the pandemic – it was a hindrance to our ability to handle the pandemic.”

• Covid inquiry
• Nicola Sturgeon
• Boris Johnson
• Scottish politics
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