The prime minister's former top aide said it was the attitude of Mr Johnson's now-wife Carrie Symonds that forced him to consider a coup, saying she wanted to pull the strings rather than the government.
"Carrie’s view was and is the prime minister doesn’t have a plan and he doesn’t know how Whitehall works, someone is going to settle the agenda, it can either be the civil service or it can be Dominic and the Vote Leave team or it can be me ," Mr Cummings told the BBC.
He went on: "As soon as the election was won her view was why should it be Dominic and the Vote Leave team? Why shouldn’t it be me that’s pulling the strings?”
Mr Cummings said that in mid-January, just weeks after Mr Johnson's emphatic general election win, that the PM's top team of advisers were "having meetings in Number 10 saying it’s clear that Carrie wants rid of all of us".
"At that point we were already saying by the summer either we’ll all have gone from here or we’ll be in the process of trying to get rid of him and get someone else in as prime minister.”
He added: "Within days we were in a situation where the prime minister’s girlfriend is trying to get rid of us and appoint complete clowns to certain key jobs.”
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A Number 10 spokesperson told the BBC: “Political appointments are entirely made by the prime minister.”
Sticking the knife into his former boss, the political strategist said Mr Johnson "doesn’t have a plan, he doesn’t know how to be prime minister and we only got him in there because we had to solve a certain problem not because he was the right person to be running the country.”
The former prime minister's former chief adviser was speaking to the BBC as part the broadcaster's TV programme "Dominic Cummings: the interview, BBC two".