Mark Drakeford said he felt a “sense of despair” and was “wringing” his hands after a crisis meeting with the prime minister, following France’s travel ban on crossing the Channel.
On the Zoom call, Mr Johnson said he wanted to “urgently look at the implications of the travel bans that some of our European friends have imposed”.
A TV documentary cuts away from most of the meeting – which cannot be recorded for security reasons – but Mr Drakeford is then heard to say: “Dear me, he really, really is awful.
“Imagine that some deadly new variant of the virus had been discovered in France and they were trying to persuade us that there was no need to take any action to stop French lorry drivers from driving across the continent.”
The pre-Christmas ban on passengers and freight entering from the UK sparked chaos in Kent, triggering many miles of queues for lorries and travellers.
France later eased the crackdown after an agreement was struck to have lorry drivers tested and allowed to cross if they returned negative results.
Asked by an adviser whether he wanted any minutes from the meeting, Mr Drakeford said: “No, I don’t think there is anything at all, other than wringing our hands, a sense of despair. Difficult to understand.”
The comments are revealed after Mr Drakeford lashed out at Mr Johnson for putting the Union at threat by failing to create effective working by the devolved administrations.
“The Union, as it is, is over,” he told a committee of MPs last week. “There is no institutional architecture to make the United Kingdom work. It is all ad-hoc, random and made up as we go along.”
In the S4C documentary, the first minister said he and Mr Johnson are “very different people – despite both studying Latin – adding: “It’s hard to find anything else that’s common between us as people.
“The world through Boris Johnson’s eyes is so different to the world that people in Wales see. It’s difficult sometimes to understand where he’s coming from and why he’s doing what he’s doing.”
The programme also shows the decision-making that led to Wales to allow only two households to mix over Christmas – not the three originally agreed across the UK.
Amid confusion over whether that would be guidance or law, Mr Drakeford said of the media: “Let’s hope nobody is bright enough to ask, ‘is that ‘should’ as in regulation or ‘should’ as in advice’?
“They are asking already”, an official tells him – prompting the first minister to say “shit” in response.
A later cabinet meeting shows ministers were split over whether to make the rule legally enforceable, but Mr Drakeford decided to go ahead, putting the guidance into law.