Matt Hancock urged the Government to argue that the UK was “better prepared than other countries” for a pandemic only a day before he claims to have called for an immediate lockdown, the UK Covid-19 Inquiry has heard.

Giving evidence to the inquiry on Thursday, the former health secretary said he told then-prime minister Boris Johnson that a lockdown was necessary on March 13 2020, 10 days before a lockdown was eventually announced.

But inquiry barrister Hugo Keith KC questioned his claim, saying there was no entry in Mr Hancock’s book, Pandemic Diaries, recording such a conversation and no notes or emails in the inquiry’s possession to back up his version of events.

Mr Keith said: “It’s not in your diary, so-called, I should say, Mr Hancock. The entry for March 13 makes no reference to you telling the prime minister this vital piece of information that he should lock down immediately.”

Reading from the former health secretary’s book, Pandemic Diaries, the lawyer said: “There is a whole page on how you woke up for the dawn flight to Belfast … there was from the prime ministerial meeting, prime ministerial papers, a video call and according to your book you said: ‘I called the prime minister and told him we’d have to do some very rapid back-pedalling on the issue of herd immunity, then rang Patrick who promised to do his best to repair the damage’.”

Although it is styled as a diary, Mr Hancock’s book was written after the pandemic but “constructed” from contemporaneous material.

Mr Keith added: “Telling the prime minister of this country for the first time that he had to call an immediate lockdown is surely worthy of some recollection, is it not?”

Mr Hancock replied: “I didn’t have full access to my papers for the writing of that, and this came to light in researching the papers ahead of this inquiry.”

On Thursday, Mr Hancock was also shown a WhatsApp message he sent to then-Downing Street adviser Dominic Cummings in which he said the Government needed to “up a gear on winning the public argument”.

This included telling the public that “we are better prepared than other countries” and that the UK’s “contain phase” had been “better than other countries”.

Mr Hancock said that in fact, the following day, he started to believe the argument for resisting lockdown was “running out of road”, but that the message had been a recommendation about “communications”.

Asked whether he had a responsibility to push harder to warn British citizens that a “wall of death” was coming, he said: “In my public communications you will know that I had at that point been explaining that we might have to do that, yes.

“But I’m also a team player and the Government position was ‘not yet’.”

Mr Cummings later rebuked Mr Hancock’s account in a broadside on X, formerly Twitter, accusing him of “flat out lying” by claiming to have pushed for a lockdown on March 13.

The former aide wrote: “Hancock flat out lying to Inquiry claiming he privately pushed for lockdown on 13th with PM – but admits there’s no evidence for it – and again on 14th in mtngs – when evidence from ALL others & paper trail is that he was still pushing Plan A herd immunity 13-15th – and his Perm Sec was still pushing Plan A on 18/3 to Cabinet Secretary (email uncovered by media) – the reason I physically stopped him coming to the second mtng on 14/3 was cos he was arguing AGAINST a change of plan & bullshitting everybody about herd immunity & ‘best prepared in the world’ (see evidence from multiple witnesses).”

Allies of the former health secretary said: “Cummings is not a reliable witness and this tweet is wrong. Matt called Boris on 13th, argued for lockdown on 14th and then Boris invited Matt into the smaller meeting (with the whiteboard) after Cummings had tried to exclude him.”