Boris Johnson has said he “overwhelmingly” believes he should remain in office despite public anger at the “bitter and painful” conclusions of the inquiry into raucous parties in No 10 during lockdown restrictions.

The Prime Minister said on Wednesday that he recognised people are “indignant” over the damning findings of Sue Gray’s report into law-breaking at the heart of Government, but defied fresh calls to resign.

He said he takes “full responsibility” for the scandal but sought to play down his personal involvement in the gatherings detailed in the report.

The Gray report detailed events at which officials drank so much they were sick, sang karaoke, became involved in altercations and abused security and cleaning staff at a time when millions of people across the country were unable to see friends and family.

Mr Johnson told a Downing Street press conference: “I understand why people are indignant and why people have been angry at what took place.”

Pressed on whether he ever considered resigning, he responded: “I overwhelmingly feel it is my job to get on and deliver.

“No matter how bitter and painful that the conclusions of this may be – and they are – and no matter how humbling they are, I have got to keep moving forward and the Government has got to keep moving. And we are.”

Tory MPs gave a muted response to the report but a snap poll from YouGov suggested three in five Britons want Mr Johnson to quit.

But a Conservative ally of Mr Johnson argued it would be “ludicrous” for him to resign now.

One damning new detail was the “multiple examples of a lack of respect and poor treatment” of cleaning and security staff during the events, which Ms Gray said was “unacceptable”.

Mr Johnson apologised, described their treatment as “repugnant” and “utterly intolerable”, and said he has started “to make some inquiries” to find out who was behind the behaviour.

The report said the “senior leadership” in No 10 must “bear responsibility” for the culture which led to lockdown rules being broken at a series of events in 2020 and 2021.

Ms Gray added: “The events that I investigated were attended by leaders in Government. Many of these events should not have been allowed to happen.”

The Metropolitan Police have issued 126 fines for rule breaches in No 10 and Whitehall, with the Prime Minister receiving a single fixed-penalty notice for his birthday party in the Cabinet Room in June 2020.

But senior civil servant Ms Gray condemned the wider culture that had been allowed to develop under Mr Johnson’s leadership.

She said some junior officials who attended parties “believed that their involvement in some of these events was permitted given the attendance of senior leaders”.

“The senior leadership at the centre, both political and official, must bear responsibility for this culture,” she added.

“Many will be dismayed that behaviour of this kind took place on this scale at the heart of Government.

“The public have a right to expect the very highest standards of behaviour in such places and clearly what happened fell well short of this.”

Conservative backbencher Julian Sturdy added his voice to those calling for Mr Johnson to step down, with the York Outer MP saying “it is in the public interest for him to resign”.

Former ministerial aide Angela Richardson said the scandal has eroded public trust in politicians and “reflects badly on us all”.

“I am clear that had this been a report about my leadership, I would resign,” the Tory MP wrote online.

Labour leader Sir Keir Starmer told the Commons the report “laid bare the rot” in No 10 and called on Tory MPs to tell Mr Johnson “the game is up” and that it is “time to pack his bags”.

SNP Westminster leader Ian Blackford called on the Prime Minister to resign for “orchestrating” the scenes in Downing Street.

Liberal Democrat leader Sir Ed Davey said: “Any other PM would be forced to resign by a report as damaging as this, yet still Conservative MPs defend Johnson and allow him to cling on.”

But it is Conservative MPs who will decide his fate, and Mr Johnson further apologised at a closed-doors meeting of the 1922 Committee of backbenchers.

Earlier, senior backbencher Tobias Ellwood, a prominent critic of the Prime Minister, challenged Mr Johnson over the “damning report” which revealed an “absence of leadership, focus and discipline in No 10”.

He asked fellow Tories “Are you willing day in and day out to defend this behaviour publicly?” and “Can we win the general election on this current trajectory?”

The inquiry’s findings include:

– Staff were drinking in No 10 until the early hours of the morning on the eve of the Duke of Edinburgh’s funeral, with the last departure recorded at 4.20am.

– Mr Johnson joined five advisers in a “food and alcohol” event in his Downing Street flat on the evening of the announcement of Dominic Cummings’ departure as chief adviser.

– Then-proprietary and ethics chief Helen MacNamara provided a karaoke machine for a Cabinet Office gathering where one individual was sick and there was a “minor altercation” between two others.

– Then-senior adviser to the Prime Minister Martin Reynolds boasted “we seem to have got away with” a bring-your-own-booze garden party in a WhatsApp message to a special adviser.

– Mr Johnson brought cheese and wine from his own flat to a garden gathering on May 15 2020.

The report includes a series of photos, with Mr Johnson pictured at the surprise birthday party in the Cabinet Room on June 19 2020 for which he received a fine.

He is seen with Cabinet Secretary Simon Case and Chancellor Rishi Sunak, with sandwiches, juice and what appears to be lager. In one picture Mr Johnson is seen raising a can of beer aloft.

Other photos include previously seen images of Mr Johnson raising a glass of wine at a leaving do for his former spin doctor Lee Cain on November 13 2020.

In a Commons statement, Mr Johnson repeated his apology over the birthday party and added: “I take full responsibility for everything that took place on my watch.

“Sue Gray’s report has emphasised that it is up to the political leadership in Number 10 to take ultimate responsibility and, of course, I do.”

Mr Johnson said he was “humbled” by the experience and had learned his lesson.