Boris Johnson “is going nowhere” and “retains the confidence of the people of this country”, a minister has claimed, as pressure mounts over Downing Street holding a “bring your own booze” party during the first COVID lockdown.

The prime minister and his wife Carrie are understood to have been among 40 people in attendance at the event in the Downing Street garden on 20 May 2020, when outdoor gatherings were banned in England.

Answering an urgent question tabled by Labour about the party, Paymaster General Michael Ellis told MPs he has “confidence” in Mr Johnson’s “integrity and honour”.

Facing relentless heckles and laughter from opposition benches in the Commons, Mr Ellis said the PM “takes this matter very seriously” and repeated that an investigation is taking place which will include the gatherings on 15 May and 20 May 2020.

Senior civil servant Sue Gray is leading the ongoing inquiry into multiple allegations of COVID rule-breaking in Downing Street and other government buildings.

“It will establish the facts and if wrongdoing is established there will be requisite disciplinary action taken,” Mr Ellis said of the investigation, adding that it “would not be appropriate” for him to comment further while it is ongoing.

To further laughter, Mr Ellis told the Commons: “It is clear that in this country the same rules apply to everyone.”

“The prime minister is going nowhere. He retains the confidence of the people of this country,” the paymaster general later added when asked directly if such a gathering in the Downing Street garden would have broken the government’s own coronavirus rules in place at the time.

But Labour’s deputy leader Angela Rayner, who had asked the PM to answer the urgent question, said Mr Johnson’s absence from the Commons “speaks volumes”.

“I think his absence speaks volumes as does his smirks on the media, the public have already drawn their own conclusions. He can run but he can’t hide,” Ms Rayner said, adding that there is “no need for an investigation”.

“If the prime minister was there, surely he knew,” she continued.

In response, Mr Ellis said “there is a need” for an investigation “and that need is clear”.

“She asks if I have confidence in the prime minister’s integrity and honour, and I do,” he added.

Labour MP Dame Angela Eagle later quipped: “Perhaps it would be faster if Sue Gray were to investigate the days there weren’t parties.”

Mr Ellis said the results of Ms Gray’s inquiry will be in the public domain “in due course”.