Downing Street under Boris Johnson is “a branch of the entertainment industry” and nothing will get done in terms of serious policy focus until he leaves, Dominic Cummings has said in his latest blast at his former boss.

In a question and answer session with paid subscribers to his Substack newsletter, Johnson’s former chief adviser described the prime minister as “a pundit who stumbled into politics and acts like that 99% of the time”.

Giving evidence to MPs last month, Cummings criticised Johnson as completely unfit to be prime minister, describing him as media obsessed and “like a shopping trolley smashing from one side of the aisle to the other”.

On Monday, answering a question on the potential cybersecurity threat to the UK if another country develops human-level artificial general intelligence, or AGI, Cummings wrote that this would be huge, potentially giving those with AGI “the power to subdue everyone – and destroy us all”.

Cummings said that if he had stayed at No 10 – he was dismissed in November – he would have ordered a focus on the threat, but this would not happen under Johnson.

“NOTHING like this now will get serious focus in no10 – no10 now is just a branch of entertainment industry and will stay so til BJ gone, at earliest,” he wrote.

“The most valuable commodity in gvt is focus and the PM literally believes that focus is a menace to his freedom to do whatever he fancies today, hence why you see the opposite of focus now and will do til he goes …”

Earlier in the lengthy thread, Cummings was asked if he saw Johnson more as a hedgehog or fox, a reference to a celebrated Isaiah Berlin essay that categorised people into those who inhabit one central idea and those with a broader view.

He replied: “Neither, he’s a pundit who stumbled into politics and acts like that 99% of the time but 1% not – and that 1% is why pundits misunderstand him/underestimate him.”

Among a string of answers covering everything from his admiration for the 19th-century German statesman Otto von Bismarck to lessons from the 2016 Vote Leave campaign, Cummings also talked about what he had learned from proximity to power.

He wrote: “When you watch the apex of power you feel like, ‘If this were broadcast, everyone would sell everything and head for the bunker in the hills’.

“It’s impossible to describe how horrific decision-making is at the apex of power and how few people watching it have any clue how bad it is or any sense of how to do it better, it’s generally the blind leading the blind with a few non-blind desperately shoving fingers in dykes and clutching their heads …”

Cummings found time to further insult Matt Hancock, having claimed during his evidence to MPs that the health secretary lied to colleagues amid the Covid pandemic, later releasing screenshots of a message in which Johnson called Hancock “totally hopeless”.

Asked by one reader about some statements made by Hancock about Covid, and whether these revealed a particular philosophical approach within government, Cummings said: “Hancock just says nonsense things all the time, I would not infer there is some complex moral reasoning going on!”