British Prime Minister Boris Johnson thought attending a party in the garden at No 10 Downing Streets was "part of his work to motivate" his workforce, Education Minister Nadhim Zahawi said.
Bu the prime minister has insisted that he "believed implicitly that this was a work event".
"I think the reason that he clearly wanted to apologise was because he implicitly thought that this was part of his work to motivate his team," Mr Zahawi told ITV.
"With the benefit of hindsight and reflecting on the events of that day, he rightly said he regrets that deeply, apologised for it and showed, I think, real contrition that it was a real mistake."
He said now that Mr Johnson had apologised, the public must await "the detail".
"I think the detail will come with Sue Gray's report and investigation," Mr Zahawi said.
When asked how the party, to which a leaked email invited more than 100 recipients to "bring their own booze", could possibly be seen as work, Mr Zahawi continued to defend his boss.
"No 10 Downing Street is a big department as well as being home to the prime minister, and I think when you frame the question as 'how is it work going out in your garden at home', well No 10 is a big workplace," he said.
Four Conservative MPs have now called for Mr Johnson to resign but many Cabinet ministers have rallied behind him publicly.
Senior Conservatives flooded broadcast studios and social media with praise for the prime minister after his admission that he attended the party in May 2020 and fears over a Conservative revolt rose.
Culture Secretary Nadine Dorries was the first to back her boss, saying an inquiry led by senior official Sue Gray must be allowed to go ahead.
Ms Dorries wrote on Twitter that the "PM was right to personally apologise earlier.
"People are hurt and angry at what happened and he has taken full responsibility for that. The inquiry should now be allowed to its work and establish the full facts of what happened."
Responding to her message, Levelling Up Secretary Michael Gove said: "Nadine is right."
A former leadership hopeful, Mr Gove also supported Mr Johnson to the 1922 Committee of backbench Tory MPs, where he is reported to have said Mr Johnson "gets the big calls right" and urged colleagues not to be "flaky".
Chancellor Rishi Sunak said on Twitter: "The PM was right to apologise and I support his request for patience while Sue Gray carries out her enquiry."
After speculation over why he had not publicly supported Mr Johnson earlier, he said: "I've been on a visit all day today continuing work on our Plan For Jobs, as well as meeting MPs to discuss the energy situation."
Foreign Secretary Liz Truss said: "I stand behind the Prime Minister 100 per cent as he takes our country forward."
Deputy Prime Minister and Justice Secretary Dominic Raab told ITV it was a "daft question" when asked whether he would run again for the Tory leadership.
"I'm fully supportive of this Prime Minister and I'm sure he will continue for many years to come," Mr Raab said.
"I completely understand why people feel let down. The PM did the right thing by apologising," said Health Secretary Sajid Javid.
"I think the Prime Minister was very contrite today. He apologised and he took full responsibility," Transport Secretary Grant Shapps told Times Radio.
"I think the Prime Minister has got things right again and again and again," Commons leader Jacob Rees-Mogg told the broadcaster.
"But like us all, he accepts that during a two-and-a-half-year period, there will be things that with hindsight would have been done differently."
Asked if the PM would resign if Ms Gray's report found wrongdoing, Environment Secretary George Eustice said: "I don't think we should get ahead of ourselves here. We should take this a step at a time."
Defence Secretary Ben Wallace backed the PM, as did International Trade Secretary Anne-Marie Trevelyan and Chancellor of the Duchy of Lancaster Steve Barclay.
Work and Pensions Secretary Therese Coffey, Conservative Party chairman Oliver Dowden, Attorney General Suella Braverman and Cop26 President Alok Sharma also threw their support behind Mr Johnson.