At least 50 more fines have been issued as a result of the police investigation into lockdown-breaking parties in Downing Street and Whitehall during coronavirus restrictions.

But Number 10 has confirmed Prime Minister Boris Johnson is not one of those who have received a new fixed penalty notice (FPN).

In the latest update on its investigation, the Metropolitan Police said as of Thursday it has made more than 100 referrals for FPNs to the ACRO Criminal Records Office for breaches of COVID-19 regulations.

Three tranches of fines had been issued previously, with 20 announced in the first wave at the end of March and more than 30 in April, meaning there are at least 50 FPNs in the latest wave.

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The identities of those who receive fines are not revealed by police, as is normal practice with the issuing of fixed penalty notices.

However, Downing Street has made clear they would make it public if further fines are received by the prime minister, the chancellor or the cabinet secretary.

When the second set of fixed penalty notices was revealed in April, it was quickly confirmed that the PM, his wife Carrie and Chancellor Rishi Sunak were among those penalised for breaking the government’s own COVID laws in a scandal that has been dubbed “partygate”.

Read more: All you need to know about the Met Police’s partygate investigation

All three were hit with the £50 penalty for their attendance at a birthday party for the PM in the Cabinet Room in Downing Street on 19 June 2020.

They have all since paid the fine.

It meant Mr Johnson became the first sitting prime minister to receive a punishment for breaking the law.

Responding to the news that the Met Police has now issued 100 fines over partygate, Liberal Democrat Leader Ed Davey said: “Boris Johnson stood up in parliament and said COVID rules were followed in Number 10 at all times.

“Now 100 fines have been issued by the police over partygate. It shows the shocking scale of the law-breaking in Johnson’s Downing Street and the extent of his lies.”

But the culture secretary and the education secretary said they still have faith in Mr Johnson despite the number of COVID fines in Whitehall and Downing Street passing 100.

Nadine Dorries and Nadhim Zahawi were asked the question before a cabinet meeting at a pottery in Staffordshire. The culture secretary said “we do” and Mr Zahawi said “absolutely”.

Meanwhile, Labour leader Sir Keir Starmer and his deputy Angela Rayner are currently under investigation by Durham Police over whether an event with party activists in April last year broke COVID rules.

The inquiry was launched after footage emerged of him drinking a beer with colleagues in April 2021 when restrictions were in place.

Both have said they will resign if they are fined by the force.

Sir Keir has accused Conservative MPs of “mudslinging” over the issue.

Labour has rejected that there is any equivalence with the Downing Street partygate scandal, which has rocked the government and is confident the party can prove Sir Keir did not break lockdown rules.

The developments in April renewed calls from opposition parties for the PM to resign – with the chancellor also facing pressure to quit – but Mr Johnson’s position appeared to be safe in the short term.

Although Lord Wolfson quit as justice minister, Mr Johnson’s cabinet has given its backing to the PM.

Some Tory MPs have said the PM should go now, but Mr Johnson’s response to Russia’s invasion of Ukraine seems to have shored up his position and caused some of his backbenchers to rethink their demands for his departure from Number 10.

Further fines for the PM could change this, however.

Mr Johnson has offered a “full apology” for breaking his own COVID rules, but has said he will not be resigning.

Despite further rumblings of discontent within his own party over lockdown-busting parties that took place across Downing Street and Whitehall, the PM was adamant last month that he will still be prime minister in six months’ time.

In April, Conservative MP Robert Largan became the latest of more than a dozen of the PM’s own backbenchers to call for him to resign.

Mr Largan told constituents in a newsletter that he “will not defend the indefensible”.

Earlier in the same week, former minister Steve Baker, an influential Conservative MP, said the prime minister “should be long gone”.

Meanwhile, fellow Conservative MP and Public Administration and Constitutional Affairs Committee chairman, William Wragg, confirmed he had submitted a letter of no confidence in Mr Johnson’s leadership.

The Metropolitan Police’s investigation into lockdown-breaching parties held across Downing Street and Whitehall is still ongoing.