In a stinging rebuke over how the health secretary handled the early stages of the coronavirus pandemic, the prime minister's former top aide pulled few punches in what he thought of the minister's performance.
Mr Cummings said many public servants fell "disastrously below the standards which the country expects" when it came to the handling of the pandemic and singled out Mr Hancock as one of those people.
He said the health secretary should have been fired for "at least 15-20 things, including lying to everybody on multiple occasions".
He told the committee: "I said repeatedly from February and March if we don't fire the secretary of state and if we don't get the testing in someone else's hands we are going to kill people and it's going to be a catastrophe."
He also said: "Pretty much every senior person around Number 10 told him that we can’t go into the autumn with the same system in place, otherwise we are going to have a catastrophe on our hands.”
Later on, Mr Cummings claimed Mr Johnson came close to sacking Mr Hancock in April and added there "was no good reason for keeping him".
Mr Cummings also told the committee the cabinet secretary said to the prime minister in one of the first meetings he had after recovering from Covid-19 the British system "is not set up to deal with a secretary of state who repeatedly lies in meetings".
A lot of Mr Cummings focus was on Mr Hancock's priorities when it came to coronavirus testing, the aim of reaching 100,000 tests a day and the establishment of the test and trace service.
He said the test and trace system should have been set up in January but when moves were being made to establish it in April “the system was hugely distracted” by Matt Hancock’s promise to increase testing to 100,000 a day across the UK.
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He also said between January and roughly mid-March everyone was thinking there would be her immunity by September so there was no need to build test and trace.The former aide said after he returned to work after suffering from Covid he started "getting calls saying Hancock is interfering with the building of the test and trace system because he’s telling everybody what to do to maximise his chances of hitting his stupid target by the end of the month".
Cummings told the committee: “We had half the Government with me in No10 calling around frantically saying do not do what Hancock says, build the thing properly for the medium term.
“And we had Hancock calling them all saying down tools on this, do this, hold tests back so I can hit my target.
“In my opinion, he should’ve been fired for that thing alone."
He said the focus on the 100,000 tests a day target "hugely disrupted" parts of Whitehall "because Hancock wanted to be able to go on TV and say ‘look at me and my 100k target’".
“It was criminal, disgraceful behaviour that caused serious harm.”
The government did hit the 100,000 tests a day target by the end of April 2020 but faced accusations of fiddling with the numbers to inflate the figures as the deadline drew near.
Mr Cummings added Mr Hancock's behaviour was one of the reasons the test and trace system was taken away from the Department of Health and a new agency set up.
He also said he told the prime minister in July he was going to leave his role by December 18 because the government was too chaotic - he eventually left on November 13.
He said he told the prime minister: "I am not prepared to work with people like Hancock any more, I have told you umpteen times you have got to remove him, you won’t, it’s going to be a disaster in the autumn and therefore it’s time that I should go.
"He laughed and said 'you’re right, I am more frightened of you having the power to stop the chaos, chaos isn’t that bad, chaos means that everyone has to look to me to see who’s in charge'."
Chairman of the health select committee Jeremy Hunt said Mr Cummings had raised “very serious allegations said under parliamentary privilege” about Mr Hancock's behaviour and the health secretary would have a chance to respond to them when he appeared before the committee in a fortnight.
However, Downing Street has declined to deny that the Prime Minister considered sacking Matt Hancock in April last year but insisted Boris Johnson has confidence in the Health Secretary now.
Asked about Dominic Cummings’ allegation, the Prime Minister’s official spokesman said: “I don’t plan to get into every allegation or claim made today.
“At all times the Prime Minister and the Health and Care Secretary have been working closely to protect public health during the pandemic, that’s been the case throughout and continues to be so.”
A spokesman for the Secretary of State for Health and Social Care said: “At all times throughout this pandemic the Secretary of State for Health and Social Care and everyone in DHSC has worked incredibly hard in unprecedented circumstances to protect the NHS and save lives.
“We absolutely reject Mr. Cummings' claims about the Health Secretary.
“The Health Secretary will continue to work closely with the Prime Minister to deliver the vaccine rollout, tackle the risks posed by variants and support the NHS and social care sector to recover from this pandemic.”