- Theresa May's Conservatives lost majority in the UK election yesterday
- The aides are accused of creating a 'toxic' atmosphere in Downing Street
- Mr Timothy took responsibility for the much-criticised Tory manifesto
Senior members of the ruling Conservative party had reportedly made the departure of Nick Timothy and Fiona Hill a condition of allowing May to stay on after losing her parliamentary majority in Thursday's vote.
But it will be another blow to the prime minister, who has been heavily reliant on their advice and support since her previous job at the interior ministry.
Timothy said he had resigned on Friday after the result was confirmed, and took responsibility for the Conservative manifesto, including a botched plan for elderly social care that caused a major backlash.
But he wrote on the ConservativeHome website: "The reason for the disappointing result was not the absence of support for Theresa May and the Conservatives but an unexpected surge in support for Labour."
A party spokesman confirmed Hill had also resigned.
Timothy and Hill have been accused of creating a "toxic" atmosphere in Downing Street.
May's former director of communications, Katie Perrior, had earlier recounted the "terrible" atmosphere at meetings attended by the pair, whom she said showed no respect for other staff or even ministers.
"I felt what the prime minister needs when you're going through a tough time like negotiating Brexit is diplomats, not street fighters," Perrior, who quit before the election, told BBC radio.
"They really only know one way to operate and that's to have enemies and I'm sure I'm one of those this morning."
The Conservative-backing Daily Telegraph newspaper had earlier warned: "Mrs May must accept that the result is an indictment of the furtive way she does business.
"She needs to be more collegiate, seeking the advice of the cabinet and backbench MPs while reducing her almost total reliance on a tiny cadre of advisors."
Timothy had been widely blamed for the social care plan, over which May was forced to backtrack in the middle of the election campaign following signs it was hitting the party's core support.
Hill has also made enemies with her combative style, confronting anyone -- including staff, ministers and journalists -- who seemed less than loyal to her boss.
Sky News anchor Adam Bolton read out a text message she had sent to him live on air after he mentioned the health of the prime minister, who has diabetes.
"Tell Bunter (Bolton) that he should watch what he says about my boss's health. Utterly unfounded and untrue. We will be making a formal complaint," she wrote.
Last December, Hill also told senior Conservative lawmaker Nicky Morgan to keep away from Downing Street after criticising the premier for her expensive leather trousers.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)