The toll is now close to 128,000.
A mass vaccination campaign that started in December has brought infections and fatalities down sharply, but the government acknowledges it will have to answer serious questions at a future public inquiry.
The former Downing Street adviser had brought Mr Warner into Downing Street after he played a key role in the data-driven models used by Vote Leave's victorious European Union referendum campaign in 2016. "He described it as the new swine flu".
Cummings told MPs: "Just before the Prime Minister and I were diagnosed with having Covid ourselves, the secretary of state for health told us in the Cabinet Room "everything is fine on PPE, we've got it all covered, etc, etc".
"Lots of people were literally skiing", Cummings said.
"If we'd had the right preparations + competent people in charge, we would probably have avoided lockdown1, *definitely* no need for lockdowns 2&3", he said.
"The truth is that senior ministers, senior officials, senior advisers like me, fell disastrously short of the standards that the public has a right to expect of its government in a crisis like this".
"The prime minister regarded this as just a scare story", Cummings said, adding the view of officials was Johnson's attitude was "don't worry about it and I'm going to get Chris Whitty to inject me live on TV with coronavirus".
Initially a shadowy figure, Cummings made headlines in May 2020 when newspapers revealed he had driven 250 miles (400 kilometers) across the country after contracting COVID-19, despite a nationwide stay-at-home order.
"I take full responsibility for everything that has happened", Johnson told lawmakers on Wednesday.
He said in February his wife had told him there was a gang outside the family home "saying they're going to break into the house and kill everybody inside", and it was decided with the Cabinet Office after that - combined with press coverage with prompted more threats - that he would move his family out of London to his parents' home in County Durham regardless of lockdown rules. "As I've said before".
In recent days, Cummings has used Twitter to direct a torrent of criticism at his former employer.
In further damning testimony, Cummings outlined the "insane" situation on 12 March in which people in government were consumed with completely separate matters as the looming crisis approached.
He said Wednesday that the government believed - wrongly, it turned out - that the British public would never accept strict lockdown measures, and that locking down would simply lead to a later, steeper peak in deaths.
But he suggested the Government's policy until mid-March of pursuing herd immunity had meant officials had previously thought that testing the population at large was pointless.
Cummings, who left the government late previous year, has said the British health ministry was a "smoking ruin", that Western governments failed during the crisis, and that the secretive British state was woefully unprepared for the pandemic. Hancock is due to give his own evidence to lawmakers next month.
Cummings claimed that he, then Cabinet Secretary Mark Sedwill, and other senior government officials advised the Prime Minister to sack Hancock. The Cabinet Secretary came back to me and said "this is completely untrue, I've lost confidence in the Secretary of State's honesty in these meetings". "He was there at the time - what his motives would be I will leave to others".
The allegation came during a hearing that saw Mr Cummings begin his evidence to MPs by apologising for the Government's failures during the coronavirus pandemic. Johnson eventually imposed a nationwide lockdown on March 23, and was hospitalized in intensive care with the virus in April 2020.
'I can completely understand why people think it's weird.
"It was completely insane that I should have been in such a senior position", he reflected.