Tory MP Angela Richardson has announced she has quit as a ministerial aide to Michael Gove, sharing her "deep disappointment" at the handling of the partygate row.
The move comes after senior civil servant Sue Gray released her report into events in Downing Street earlier today.
Despite featuring minimal information about the 12 gatherings now being examined by the Metropolitan Police, Prime Minister Boris Johnson and other senior ministers were blasted for "failures of leadership and judgement" in the account.
In a Facebook post, Ms Richardson spoke of her "deep disappointment" as she revealed she has stepped back from governmental responsibilities.
She said: "Sue Gray's report published today clearly states that there were failings at Number Ten Downing Street that let us all down.
"I share the deep disappointment that it has taken so long to get to this stage when there could have been an early acknowledgement and apology.
"Last week, I stepped back from my governmental responsibilities to invest more of my time realising the campaigns that I am working on for the people of Guildford, Cranleigh and our villages.
"In so doing, I will have more freedom to fulfil my promise to you as I hold the government to account, as a critical friend, on the issues that matter most to the people of Guildford."
A number of constituents supports her decision, commenting positively on her Facebook page.
One said: "Thank you Angela. As always you are honest, clear and understand the anger felt by everyone. I admire your stepping back to come alongside your residents.
"In Nov 2020 I lost my husband of 50 years to COVID caught in St Peter’s. He was in hospital for 5 weeks and I couldn’t see him. He died alone without his family around him though the staff were wonderful.
"I don’t think No 10 has any idea what anguish and suffering was had by so many and I for one will not forget or understand why anyone would still support the leadership."
Senior Tories lined up to criticise the PM in a stormy Commons session today, in a sign of danger for Mr Johnson, who is battling to save his leadership.
The Prime Minister apologised and insisted "I get it and I will fix it" as he faced fresh calls to resign after Ms Gray's limited inquiry criticised "failures of leadership and judgement" in No 10.
The damning nine-page update said "at least some" of the gatherings were "a serious failure to observe not just the high standards expected of those working at the heart of Government, but also of the standards expected of the entire British population at the time."
Ex-PM Theresa May said Boris Johnson either ignored the rules or hadn't read or understood them - while Tory ex-Cabinet minister Andrew Mitchell said: "He no longer enjoys my support".
Tory MP Aaron Bell told Boris Johnson he drove three hours to his grandmother’s funeral in May 2020, adding: “I didn’t hug my siblings, I didn’t hug my parents, I gave a eulogy.
"Afterwards I didn’t even go to her house for a cup of tea… Does the Prime Minister think I’m a fool?”
Ms Gray warned she has “extensive substantive factual information” after interviewing more than 70 people and checking e-mails, WhatsApps, texts, photographs, official records and entry and exit logs.
And police revealed Ms Gray had gathered, and given to them, "well over 500 pieces of paper, about a ream and a half, and over 300 photographs".
Earlier tonight Downing Street confirmed it will publish a second Sue Gray report after the Scotland Yard probe ends.
