During a seven-hour joint session of the Commons Heath, and Science and Technology committees, Mr Cummings made a number of allegations - here are the key points.

1. The government 'failed'

"Tens of thousands of people died, who didn't need to die," Mr Cummings said.

Earlier, he said sorry for ministers, officials and advisers "like me" for falling "disastrously short of the standards that the public has a right to expect".

"When the public needed us most the government failed," he added, apologising to "the families of those who died unnecessarily".

Mr Cummings said the government was not on a "war footing" when the virus emerged in January and February last year and "lots of key people were literally skiing".

2. PM 'not fit for office'

Mr Cummings made a series of allegations against his former boss Boris Johnson, including:

*  He dismissed the emerging coronavirus as "the new swine flu" and "just a scare story" - and pledged to be injected "live on TV with the virus so everyone realises it's nothing to be frightened of'"

*  He was a "thousand times too obsessed with the media" and appeared to be persuaded by the Daily Telegraph's view of events on any given day

*  He said he would rather see "bodies pile high" than order a third lockdown in the autumn of 2020, seeming to confirm a BBC report and contradict the prime minister's denials

Describing a decline in his relationship with Mr Johnson after the summer of 2020, he said "it was clear in July that our relations were very far from where they had been".

He added: "They took another terrible dive after the second lockdown in October because the prime minister knew that I blamed him for the whole situation - and I did - and by 31 October our relations were essentially already finished...

"The heart of the problem was, fundamentally, I regarded him as unfit for the job. And I was trying to create a structure around him to try and stop what I thought would have been bad decisions, and push things through against his wishes."

Asked later by Labour MP Sarah Owen whether Boris Johnson was a "fit and proper person to get us through this pandemic", Mr Cummings replied: "No."

Downing Street rejected many of the remarks and Mr Johnson insisted his government at "every stage tried to minimise loss of life".

3. Hancock 'should have been fired'

Mr Cummings appeared to reserve his harshest criticism for Health Secretary Matt Hancock.

Mr Hancock "should have been fired for at least 15 to 20 things", Mr Cummings said, as he alleged the health secretary:

*  Displayed "criminal, disgraceful behaviour" as he held back coronavirus tests and meddled in efforts to build a mass testing system in order to meet a "stupid" pledge of 100,000 tests per day in April 2020

*  Lied during meetings held in the Downing Street cabinet room, including about testing people before they were discharged from hospital into care homes during the first wave

*  Used the UK's chief scientific adviser Sir Patrick Vallance and chief medical adviser Chris Whitty as a "shield" for government failings at Downing Street news conferences

*  Mr Cummings and the UK's then most senior civil servant Sir Mark Sedwill recommended to the prime minister that Mr Hancock be sacked in April 2020

*  The prime minister did not sack Mr Hancock because some felt he would be a convenient fall guy during any future public inquiry

A spokesman for Mr Hancock later said: "We absolutely reject Mr Cummings' claims about the health secretary."

Mr Hancock added he had not seen Mr Cummings' evidence to MPs in full "and instead I've been dealing with getting the vaccination rollout going, especially to over-30s, and saving lives".

He said he would make a statement in the Commons on Thursday when he would "have more to say".

4. First lockdown delay

Mr Cummings said it was "obvious" in retrospect that the UK should have locked down in the first week of March at the latest - and it was a "huge failure" on his part not to alert the prime minister.

"I bitterly regret that I didn't hit the emergency panic button earlier then I did," he added.

Mr Cummings said that, on 14 March, Boris Johnson had been told that models showing the peak of infections was "weeks and weeks and weeks away" in June were "completely wrong".

Mr Cummings said that meeting came after the then deputy cabinet secretary, Helen MacNamara, relayed concerns that there was "no plan... we're in huge trouble".

He said the PM was warned: "The NHS is going to be smashed in weeks. Really we've got days to act."

Mr Johnson announced a national lockdown nine days later on the evening of 23 March.

5. Bombs, quarantine... and Dilyn

Mr Cummings painted a vivid picture of the chaotic atmosphere in Downing Street on one "crazy" day in March 2020 when the government was considering a national lockdown - at the same time as officials considered a bombing campaign in Iraq.

One morning, he claimed, the "national security people came in" and said "[US President Donald] Trump wants us to join a bombing campaign in the Middle East tonight" and this "totally derailed" meetings about quarantine and the coronavirus.

At the same time, he said, "the prime minister's girlfriend was going completely crackers" over a story in Times newspaper with the headline "Downing St dog to be reshuffled".

The article reported a Whitehall source as saying they were not sure Carrie Symonds' dog Dilyn would "make it through the next reshuffle" due to the mess he had created in her and Mr Johnson's No 11 flat.

Mr Cummings said: "So, we have this sort of completely insane situation in which part of the building was saying, 'are we going to bomb Iraq?', part of the building was arguing about whether or not we're going to do quarantine or not do quarantine, the prime minister has his girlfriend going crackers about something completely trivial."

6. 'Chicken pox parties'

Mr Cummings said that, as late as 12 March last year, the UK's top civil servant championed a plan of rapid herd immunity involving "chicken pox parties" for the virus.

Then cabinet secretary Sir Mark Sedwill is alleged to have suggested to Mr Johnson: "Prime minister, you should go on TV tomorrow and explain the herd immunity plan and that it is like the old chicken pox parties. We need people to get this disease because that's how we get herd immunity by September."

But Mr Cummings said he told him not to use the analogy, which was "not right", as - according to data expert Ben Warner - Covid was "spreading exponentially and killing hundreds of thousands of people".

7. PM 'ignored' second lockdown advice

Asked about more recent decisions over a second lockdown in the autumn of 2020, Mr Cummings alleged Mr Johnson rejected a recommendation last September for a shorter stay-at-home order in England.

"He was ignoring the advice," he added, saying the prime minister believed he had been pushed into imposing the first one and that the economic harm done by lockdown would be worse than Covid itself.

He added: "All credible serious people in my opinion were saying essentially the same thing so I was very, very clear with him about it.

"He wasn't taking any advice, he was just making his own decisions, he was going to ignore the advice. Cabinet wasn't involved or asked.

"I've been very critical of Matt Hancock but I think Hancock agreed with me actually in September about acting then."