During his seven-hour evidence session on Wednesday, Mr Cummings told MPs that the prime minister had been told "categorically in March that people will be tested before they went back to care homes" from hospital by Mr Hancock - something which did not happen.
His claims about the prime minister and health secretary Matt Hancock rocked Westminster and tore a hole in the once seemingly close relationship between Cummings and Johnson.
"These allegations from Cummings are either true, and if so the secretary of state (Hancock) potentially stands in breach of the ministerial code ... or they are false and the prime minister brought a fantasist and a liar into the heart of Downing Street", he said.
Cummings, who masterminded the Vote Leave campaign in the 2016 Brexit referendum before joining Johnson when he became prime minister three years later, claimed that Johnson had repeatedly ignored scientific advice and wrongly delayed lockdowns.
Cummings said the health minister "should have been fired for at least 15, 20 things" after "lying to everybody on multiple occasions, in meeting after meeting in the cabinet room and publicly".
A statement from the Prime Minister is expected with the initial comments made in an interview during a visit to Colchester Hospital.
Earlier, Mr Hancock told MPs the "unsubstantiated allegations" from Dominic Cummings that he lied during the pandemic "are not true".
'Central Park Karen' Sues Former Employer for Racial Discrimination
It also claims the company's actions caused Amy Cooper to suffer "severe emotional distress" and that she was suicidal. The lawsuit alleges that Franklin Templeton "did not seek to interview Jerome Lockett or anyone else familiar with Mr.
The prime minister admitted that setting the trauma of lockdown against the horrors of Covid had been incredibly hard, but he insisted that protecting life had governed all those decisions.
Following his explosive revelations about the government's response to coronavirus, Dominic Cummings features on most of the United Kingdom front pages on Thursday. They even hid thousands of covid deaths, with just the HSE reporting 111 people have died at work whilst their own statistics, showed more than 5,000 people had died from covid.
He insisted that "at every stage we have been governed by a determination to protect life" but acknowledged the situation in care homes had been "tragic". "What people want us to get on with is delivering the (reopening) road map and trying, cautiously, to take our country forward through what has been one of the most hard periods that I think anybody can remember", he told reporters on Thursday.
Coronavirus has claimed almost 128,000 lives in the United Kingdom - the fifth-highest official death toll in the world, and the highest in Europe.
A UNION is calling for a public enquiry over the lack of strategy from the government's handling of COVID-19. Opposition politicians and families who have lost loved ones to COVID-19, want it to start sooner. Nearly three-quarters of British adults have had one dose of a coronavirus vaccine, and 45% have had both doses.
"I committed to getting the policy in place, but it took time to build the testing", he said.
"But we may need to wait".