UK Prime Minister Boris Johnson is facing pressure to quit over allegations he attended a coronavirus lockdown-busting "bring your own booze" party in the Downing Street garden.

Mr Johnson continued to support senior official Martin Reynolds, who invited colleagues to the gathering in May 2020 during England's first lockdown and has refused to say whether he attended it himself.

Downing Street said Mr Reynolds, the prime minister's principal private secretary, "continues in his role" after ITV news published the email he sent to colleagues encouraging them to bring alcohol to the event to "make the most of the lovely weather".

The leaked email, which came to light on Monday, said: "Hi all, after what has been an incredibly busy period we thought it would be nice to make the most of the lovely weather and have some socially distanced drinks in the No 10 garden this evening.

"Please join us from 6pm and bring your own booze!"

Asked whether Mr Johnson still had full confidence in one of his most senior aides, the prime minister's official spokesman said he did.

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Two opinion polls suggested people believe Mr Johnson should resign, while senior opposition politicians also called for him to quit.

There was mounting anger within the Tory ranks over the latest scandal involving Mr Johnson, whose future could now hinge on the findings of an investigation into allegations of rule-breaking parties.

Scottish Tory leader Douglas Ross said the prime minister should come clean about whether or not he was at the event.

Saying he felt "furious" when he heard reports of the party, he told the PA news agency: "I'm angry. I think that reflects what people across Scotland and the UK are feeling right now."

Mr Ross restated his view that the prime minister could not continue if he is found to have misled parliament about the so-called 'partygate' rows.

Mr Johnson will face a difficult session of Prime Minister's Questions tomorrow but dodged scrutiny in the Commons today, sending paymaster general Michael Ellis to face an urgent question instead.

The Conservative leader has refused to say whether he attended the gathering along with his now wife Carrie - although it has been widely reported he was there - insisting it was a matter for the investigation being led by senior official Sue Gray into a series of alleged rule-breaking parties held in Whitehall and Downing Street during the pandemic.

But Mr Ross said: "Nothing would undermine what Sue Gray is trying to do, for the prime minister to come out and answer a very simple question.

"Was he at the party or not?"

Two separate polls suggested the public was turning against Mr Johnson.

A Savanta ComRes study found 66% of British adults thought he should quit as prime minister, with 24% saying he should stay.

And a YouGov survey for Sky News suggested 56% believed he should go, with 27% saying he should remain.

In the Scottish Parliament, First Minister Nicola Sturgeon said Mr Johnson should resign, claiming he was "not being truthful" about his knowledge of the various parties.

Responding to opposition calls for Mr Johnson to resign in the Commons, Mr Ellis told MPs the prime minister was "going nowhere", adding that he "retains the confidence of the people of this country and he did so two years ago with the biggest majority in decades".

Mr Ellis said the Gray inquiry "will establish the facts and if wrongdoing is established there will be requisite disciplinary action taken".

The investigation could be paused if evidence emerges of a criminal offence and the Metropolitan Police decides to launch an inquiry.

Scotland Yard said it is in contact with the Cabinet Office about the latest allegation.

Labour deputy leader Angela Rayner said Mr Johnson's absence from the Commons today "speaks volumes"

Deputy Labour leader Angela Rayner said the prime minister's absence from the urgent question "speaks volumes" and "the public have already drawn their own conclusions".

The Tory benches were sparsely populated, in a possible indication of a lack of support for the prime minister's position on the issue.

Robbie Moore, Conservative MP for Keighley, told the Telegraph & Argus: "The email from Martin Reynolds infuriates me."

Mr Moore said he was "deeply angered by the thought of any illegal gatherings, parties or social events which took place at Downing Street whilst the rest of the country was in lockdown and following the rules".

Health Minister Edward Argar told the BBC: "I can entirely understand why people who've lost loved ones, or people who've just had their lives hugely disrupted by these restrictions, are angry and upset by these allegations."

Hannah Brady, of the campaign group Covid-19 Bereaved Families for Justice, whose father's death certificate was signed on the day of the "socially distanced drinks", wrote to the prime minister calling for him to say whether he attended the event.

She said: "It is a matter of common decency and respect for not only us or the British people, but the office you hold as Prime Minister of the United Kingdom, to tell us whether you attended this flagrant breach of the Government's own rules."

England was under tough coronavirus restrictions banning groups from meeting socially outdoors when the message was sent.

Read more: Timeline of alleged UK Government gatherings so far

Mr Johnson refused to say whether he was at the event when questioned by reporters yesterday.

A spokesman for Scotland Yard said: "The Metropolitan Police Service is aware of widespread reporting relating to alleged breaches of the Health Protection Regulations at Downing Street on 20 May 2020 and is in contact with the Cabinet Office."

The latest row over Whitehall parties and Mr Johnson's alleged attendance was seized on by Labour, with party leader Keir Starmer telling Mr Johnson to stop lying to the British public.

In a tweet, Mr Starmer said the prime minister's "deflections and distractions are absurd".

The Metropolitan police had tweeted on the day of the alleged "bring your own booze" event, telling people they could have a picnic, exercise or do sport outside providing you are "on your own, with people you live with, or just you and one other person".

The then culture secretary Oliver Dowden used a Downing Street press conference that day to remind the public they could "meet one person outside of your household in an outdoor, public place, provided that you stay two metres apart".