The UK chancellor was concerned the prime minister had “no plan” to tackle the surge in coronavirus infections last autumn, wrote the former Number 10 chief adviser on Monday.

Dominic Cummings dismissed suggestions that Rishi Sunak was solely responsible for the government not acting faster as England entered its second wave of the pandemic in September 2020, in a question-and-answer session on his Substack blog. He added that the chancellor had expressed worries over Boris Johnson’s handling of the crisis.

“Sunak’s view was the same as all serious people July-Oct: there is no plan just a trolley smashing side to side,” Cummings wrote. “We can’t keep telling people ‘go back to work . . . stop lockdown . . . go back to work, Covid is all nonsense . . . save the NHS etc,’ which is what PM was doing.”

He added: “[The] September decision not to act seriously was a PM decision against advice of scientists, data team, me and others in No10, it wasn’t a Cabinet decision or ‘cos of Sunak.”

By mid September 2020, coronavirus infections were doubling every seven to eight days across England, while new daily infections across the UK surpassed 3,000.

During this period, experts from the government’s Scientific Pandemic Influenza Group on Modelling (SPI-M) and Scientific Advisory Group for Emergencies (Sage) proposed a two-week circuit breaker lockdown designed to coincide with the October half-term break. This suggestion was rejected by Downing Street.

In an interview with ITV this year, Sunak said he had opposed the September proposals but said the decision was ultimately the prime minister’s to make. “Ultimately things that are bad for the economy are bad for our long-term health, as well, and our ability to fund things like the NHS,” he said.

The government subsequently announced a four-week November lockdown for residents in England on October 31, by which point there were 9,295 admitted to hospital with coronavirus across the country. When the government announced the third national lockdown in England on January 4, almost 27,000 people were in hospital with the virus in England.

Cummings also claimed that the chancellor was not opposed to the first national lockdown introduced in March last year.

In his broad-ranging Q&A session with the public and journalists, the former adviser, who has been vocal since resigning from his position in November 2020, offered his views on Westminster culture as well as government policy under Johnson’s leadership.

Cummings described No10 as a “branch of entertainment” and Johnson as a “pundit who stumbled into politics”.

Amid reported tensions between Sunak and Johnson over the prime minister’s habit of announcing funding without proper prior consultation, Cummings said Number 10 would be unlikely to “contain” spending under Johnson’s leadership.

“CONs [Conservatives] will struggle to cut spending with BJ [Boris Johnson]. But in general though, Tory MPs talk to think-tanks re cutting, they panic as soon as the media screams,” he wrote.

The former adviser said that all political parties were “rotten to the core, old decrepit entities”, and that he did not think of himself as a Conservative, adding: “My political views are ‘incoherent’ in SW1 terms.”

He added that “part of the point” of Brexit was to force the Tory party to change its way of thinking and criticised the government’s post-Brexit “Global Britain” strategy, as “a crap slogan that five years later still means nothing”.

Downing Street and the Treasury have been contacted for comment.