The former chief adviser said on Monday Mr Johnson “waved it aside” when he raised concerns over principal private secretary Martin Reynolds inviting more than 100 people to a “bring your own booze” event in the garden at Downing Street.
Mr Cummings said regarding that day alone, “never mind the string of other events”, the Prime Minister “lied to Parliament about parties” by insisting he had been assured no events had taken place that would have broken coronavirus rules.
“Not only me but other eyewitnesses who discussed this at the time would swear under oath this is what happened,” he said.
The Prime Minister has faced huge pressure to resign over the Partygate scandal that saw the Prime Minister forced to apologise and admit he attended the event at PMQs last week . He has argued he believed it was a work event that could “technically” have been within the rules.
If it is established that Mr Johnson knew in advance about the party and lied to parliament in saying he believed it was a “work event”, his position would likely become untenable
Mr Cummings says that, after Martin Reynolds sent the invitation “a very senior official replied by email saying the invite broke the rules”.
Mr Cummings claims Mr Reynolds told him he would “check with the PM if he’s happy for it to go ahead”, on 20 May 2020.
“I am sure he did check with the PM. (I think it very likely another senior official spoke to the PM about it but I am not sure)”.
Mr Johnson refused to sack Dominic Cummings over his lockdown visit to Barnard Castle in 2020 (Jonathan Brady/PA)
/ PA ArchiveMr Cummings has written on his substack blog: “The events of 20 May alone, never mind the string of other events, mean the PM lied to Parliament about parties.
“Not only me but other eyewitnesses who discussed this at the time would swear under oath this is what happened.
“On Wednesday 20 May, a senior No10 official invited people to ‘socially distanced drinks’ in the garden.
“I and at least one other spad (in writing so Sue Gray can dig up the original email and the warning) said that this seemed to be against the rules and should not happen.
“We were ignored. I was ill and went home to bed early that afternoon but am told this event definitely happened.
“In my opinion the official who organised this should anyway have been removed that summer because of his failures over covid. I said this repeatedly to the PM. The PM rejected my argument.”
It came as Conservative Party chairman Oliver Dowden said there are plans to “address the kind of culture that has allowed” alleged rule breaches.
This will include a crackdown on drinking in Downing Street, The Sunday Times reported.
On Monday, the Prime Minister’s official spokesman said Mr Johnson will set out his changes after senior civil servant Sue Gray publishes her inquiry into allegations of partying.
He told reporters: “I think I’d point back to what the Prime Minister’s talked about, that there’s a shared recognition that No 10 should be held to the highest standard.
“There are things clearly we didn’t get right and we need to take responsibility for those. But beyond that, I think it’s right to let the report be published and then you’ll hear more from the Prime Minister.”
