Dominic Raab has defended Downing Street staff who were under “incredible pressure” after police investigating the partygate scandal began to announce fines for lockdown breaches.

The deputy prime minister admitted that “there were clearly things that were got wrong” but said the prime minister had since overhauled the Number 10 operation.

Mr Raab’s comments come a day after the Met said 20 fixed penalties were set to be issued following its investigation into lockdown-breaking parties in Downing Street and Whitehall in 2020 and 2021.

Opposition politicians have called for Boris Johnson to resign over laws being broken in Number 10.

Mr Raab described what had happened as “deeply regrettable”.

But he told Sky News: “My experience was the incredible pressure and hard work and dedication of the overwhelming majority of people working in Number 10.”

Mr Raab said he agreed with the need for accountability for what had taken place, adding: “It’s not right to tar all the civil servants who have worked so hard during this pandemic.”

“I don’t accept the sort of caricature is right,” he added.

“I saw a lot of people working incredibly long hours under incredible pressure doing their very best.

“I think there clearly were things that were got wrong.

“That’s why the PM overhauled the operation in Number 10 Downing Street.

“It’s well known the individuals that have come in and the individuals, at least some of them, that have left, and that’s because he takes it so seriously and we do take it so seriously.

“Government gets things wrong and civil servants and, lord knows, politicians get things wrong as well.

“If you’re asking me what I saw during the pandemic – huge number of people working incredibly long hours under incredible pressure to do the right thing.”

Read more: Everything you need to know about the police investigation into partygate

Mr Raab also defended Mr Johnson’s initial statements that rules had not been breached, saying he was “telling the House of Commons and the public what he knew to the best of his ability” at the time.

But Labour stepped up its criticism of the PM, with shadow health secretary Wes Streeting telling Sky News: “To have a prime minister who lied to the country, to the House of Commons, to the Queen and still be in post is completely unacceptable.”

Mr Johnson was among 100 people who were sent formal legal questionnaires relating to the investigation – named Operation Hillman – which was launched in January.

After the fines were announced by the Met on Tuesday, a spokesman for the PM said Mr Johnson had not received a fine as yet but reiterated that it would be made known if that were to happen.

However the identities of other staff who receive penalties may not become known – even to the civil service and Downing Street – as they will not be asked to disclose this.

There would be an exception if Cabinet Secretary Simon Case is fined, Number 10 has said.