Dominic Cummings has accused Matt Hancock of “criminal, disgraceful behaviour” by interfering with the NHS test and trace system, adding that he urged Boris Johnson to fire him over it.

The former chief adviser told MPs the health secretary had set a “stupid” 100,000 daily target for tests by the end of April 2020, while Boris Johnson was still in hospital with coronavirus.

He said a decision was taken to remove test and trace from Mr Hancock’s control once it was realised a mass Asian-style testing system was needed.

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.

Mr Cummings said: “In my opinion, disastrously, the secretary of state had made, while the Prime Minister was on his near-death bed, his pledge to do 100,000 by the end of April.

“This was an incredibly stupid thing to do because we already had that goal internally.

“What then happened, when I came back around the 13th (of April) was I started getting calls, and No 10 were 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.

It was criminal, disgraceful behaviour that caused serious harm

“We had half the Government with me in No 10 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, and that itself meant the whole of April was hugely disrupted by different parts of Whitehall fundamentally trying to operate in different ways completely, 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.”

Mr Cummings said he warned the Prime Minister that “if we don’t fire the secretary of state (Matt Hancock) and we don’t get the testing in someone else’s hands, we are going to kill people and it will be a catastrophe”.

Mr Hancock’s behaviour over coronavirus testing was why a fresh agency was set up to handle it, he added.

“That was one of the reasons why the cabinet secretary and I agreed that we had to essentially take testing away from Hancock and put it in a separate agency.

“There was all this bureaucratic infighting in April, and remember the Prime Minister wasn’t back then either, Dominic Raab was doing a brilliant job chairing the meetings, but this was a huge call and very difficult for him to basically start carving up the Department of Health in April.

The core of the Government kind of collapsed when the Prime Minister got ill himself, because he’s suddenly gone and then people are literally thinking that he might die

“So, essentially, we never really got to grips with it until the Prime Minister was back in the office, and the cabinet secretary and I could say to him ‘we’ve got to do the track and trace thing in a completely different way’.”

Earlier, Mr Cummings said the decision to pursue herd immunity by the Government meant officials thought there was no point in March in building a comprehensive test and trace system.

Public Health England (PHE) officials have previously admitted that contact tracing was abandoned when it became apparent Britain was facing a huge outbreak of coronavirus.

Mr Cummings told MPs that “the logic was, if you go in for the optimal single peak strategy – herd immunity by September – in the same way you don’t take vaccines as a kind of urgent priority, you don’t take testing as an urgent priority, and that’s why the Department of Health said (in mid-March) ‘we don’t need to test everyone any more’, because the view was simply, well, 60% or 70% of the country or something are going to get (Covid), that’s going to happen for sure.

“Why would you even bother testing all of those different people, because we’re not going to have a test, track, isolate, quarantine system, because we’re going for herd immunity by September.

“So no-one challenged, really, that idea strongly, until we challenged it as part of the whole kind of shift-to-plan-B.

“Even in late March, PHE said officially, on the record, possibly even to this committee, I can’t remember now, ‘well, obviously there’s just no way that this country is going to do test, track and trace like they’re doing it in Asia.

“That was the… completely common assumption.”

Mr Cummings said he and chief scientific adviser, Sir Patrick Vallance, did challenge that theory but those conversations did not really happen until the decision was taken to lock down.

Asked by committee chairman, and former health secretary, Jeremy Hunt, why the testing system was not set up until the end of May, Mr Cummings said essentially “the whole core of government fundamentally fell apart” when the Prime Minister got ill with coronavirus.

He added that “the core of the Government kind of collapsed when the Prime Minister got ill himself, because he’s suddenly gone and then people are literally thinking that he might die”.

Mr Cummings also told MPs there was “constant, repeated lying” about personal protective equipment (PPE) during the pandemic.

He said this could be backed up by then Cabinet secretary Mark Sedwill, who he said told Mr Johnson “the British system is not set up to deal with a secretary of state who repeatedly lies in meetings”.

Mr Hunt said these were “very serious allegations said under parliamentary privilege” and urged Mr Cummings to provide evidence of his claims before Mr Hancock appeared in front of MPs in a fortnight.