Ms Stratton announced that she was quitting as the prime minister’s spokesperson on the Cop26 climate change summit a day after the footage – filmed in December last year – was broadcast by ITV and just hours after Mr Johnson ordered an inquiry into the alleged gathering.
Speaking to TV cameras outside her home in London, a tearful Ms Stratton offered her “profound apologies” for her remarks, but did not comment on whether the party took place.
Referring to the film, which was recorded as she practised for her planned role as No 10’s TV spokesperson, she said: “My remarks seemed to make light of rules, rules that people were doing everything to obey. That was never my intention.”
She added: “I will regret those remarks for the rest of my days, and I offer my profound apologies to all of you at home for them.
“Working in government is an immense privilege. I tried to do right by you all, to behave with civility and decency and act to the high standards you rightly expect of No 10.
“I will always be proud of what was achieved at Cop26 in Glasgow, and the progress that was made on coal, cars, cash and trees.
“This country’s and the prime minister's leadership on climate change and on nature will make a lasting difference to the whole world. It has been an honour to play a part in that.
“I understand the anger and frustration that people feel. To all of you who lost loved ones, who endured intolerable loneliness and who struggled with your businesses, I'm truly sorry.
“And this afternoon I am offering my resignation to the prime minister.”
Ms Stratton, 41, a former journalist, joined the government as director of strategic communications for Rishi Sunak in 2020.
She moved to No 10 in October last year to take up the post of press secretary, with the intention that she would become the first-ever TV spokesperson for the prime minister.
But plans for daily televised briefings were dropped following the departure of director of communications Lee Cain, who reportedly opposed her appointment, and she instead became a spokesperson for the UK’s Cop26 presidency.
The comments that led to her resignation came in a practice session for the TV briefings, recorded shortly after the alleged 18 December party.
Playing the part of a reporter asking a tough question, No 10 special adviser Ed Oldfield asked her to comment on reports of a party four days earlier.
Laughing, she replied: “I went home.”
She asked fellow Downing Street staffers “What’s the answer?” before adding: “Is cheese and wine alright? It was a business meeting ... This fictional party was a business meeting and it was not socially distanced.”
Speaking at Prime Minister’s Questions in the House of Commons on Wednesday, Mr Johnson said he was “sickened and furious” about the video, telling MPs: “I apologise for the impression that has been given that staff in Downing Street take this less than seriously.”
But Labour leader Sir Keir Starmer said that Mr Johsnon’s apology “raises more questions than answers”.
“Millions of people now think the Prime Minister was taking them for fools, that they were lied to. They are right aren't they?” he said.
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