London (CNN) British Prime Minister Theresa May appears to have begun a purge in her party after shock election results threw the future of her leadership in doubt.

May's co-chiefs of staff, Nick Timothy and Fiona Hill, announced their resignations Saturday on the Conservative Home political blog. Timothy conceded in a statement that he had failed to carry out an effective election campaign, while Hill made no mention of her performance

May suffered a humiliating blow as the "snap election" Thursday spectacularly backfired, stripping her Conservative Party of its commanding majority in Parliament. She had called the vote three years earlier than required by law, with the aim of sweeping an even greater majority for her party before Brexit talks in nine days to take the country out of the European Union.

Nick Timothy and Fiona Hill quit on Saturday in the wake of the vote.

May's attempts to form a government with support from Northern Ireland's Democratic Unionist Party (DUP) appear to be taking longer than first thought. On Saturday night, Downing Street issued a statement claiming that a preliminary deal had been reached, but hours later was forced to issue a second statement clarifying that no agreement had been finalized.

The Prime Minister is also fending off a mutiny in her own party. Conservative MPs are publicly airing their anger, some calling for her ouster and others demanding radical change in her style of leadership.

Several MPs have said they were angered by key points in the Conservatives' manifesto, the document that outlined the party's agenda.

MP says manifesto was 'arsenic'

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Nigel Evans was among Conservative MPs to call for Timothy's resignation, and said "anyone with their fingers" on the document should resign.

"It was absolute arsenic from beginning to end," Evans told CNN.

Evans confirmed that some MPs are calling for May's resignation, although he himself is not.

But he slammed May's style of governance as tone deaf to her own Cabinet ministers and MPs, whom he said were better in touch with voters on the ground.

He said the party's commanding lead in the polls of 20 percentage points at the start of the election period dramatically narrowed after the launch of the Conservatives' manifesto, which he said was "mean-spirited" in its call for a cut funding for children's school lunches and to charge the elderly more for their own care.

"The campaign was going well until the manifesto was launched. Of course, the core message was all lost because of the cacophony of noise we were making about social care, and so we were having to fight fires that we created ourselves rather than exposing the Labour Party's insane manifesto."

Katie Perrior, May's former director of communications, described an atmosphere of toxicity and intimidation by Timothy and Hill.

"The atmosphere would be great if the chiefs of staff were not there and terrible if the chiefs of staff were there," she told the BBC's Radio 4.

"We would be able to speak freely if they weren't around, and if they were around, you don't speak."

Another Conservative MP, Anna Soubry, told the BBC after the results came in that May has to "obviously consider her position" and take personal responsibility for the "dreadful" election campaign and "deeply flawed" manifesto.

She also echoed comments made by Evans and Perrior that much of the party had been shut out of the campaign.

"It was a tightly knit group, it was her group that ran this campaign and look where we are, for God's sake," Soubry said.

Timothy said in his statement that the election result was "a huge disappointment."

"I take responsibility for my part in this election campaign, which was the oversight of our policy program," he said.

Though he refuted reports he was responsible for the elderly care policy, saying it was "the subject of many months of work" among many people.

"I want to place on record my sorrow for the Conservative Members of Parliament who lost their seats, several of whom are close friends."

Hill described May as an "excellent Prime Minister" in her resignation statement. "I have no doubt at all that Theresa May will continue to serve and work hard as Prime Minister -- and do it brilliantly."

Backlash over controversial alliance

May is now looking to rule the country with less than 50% of seats in Parliament's House of Commons, and is banking on support from the DUP to be the ally that helps her party push its agenda through Parliament.

Contrary to an earlier statement which suggested May had reached a preliminary deal with the DUP, Downing Street said Saturday that such a deal had yet to be finalized.

"The Prime Minister has tonight spoken with the DUP to discuss finalizing a confidence and supply deal when Parliament returns next week," the statement said.

"We will welcome any such deal being agreed, as it will provide the stability and certainty the whole country requires as we embark on Brexit and beyond".

The DUP meanwhile said that discussion will continue into next week "to work on the details and to reach agreement on arrangements for the new Parliament."

May's courting of DUP has triggered criticism in the media and among members of her party, who have described DUP as anti-abortionist and regressive on LGBTI rights.

Ruth Davidson, a Conservative in Scotland, told the BBC she had words with May over the DUP's record on LGBT rights.

"I asked for a categoric assurance that if any deal or scoping deal was done with the DUP there would be absolutely no rescission of LGBTI rights in the rest of the UK, in Great Britain, and that we would use any influence that we had to advance LGBTI rights in Northern Ireland," said the MP, who is a lesbian.

"It's an issue very close to my heart and one that I wanted categoric assurances from the Prime Minister on, and I received [them]."

Pressure is now also coming from the public. A petition on Change.org had more than half a million signatures by Saturday afternoon, calling for May's resignation over her alliance with the DUP.

There have been few clues as to how May might shake up her administration, but the Prime Minister, who campaigned under the mantra "strong and stable," announced that she would retain five key Cabinet ministers in their posts.

Scathing media response

May came under fire during the campaign for the controversial policy on the cost of care for the elderly, dubbed the "dementia tax," and for making several U-turns on social care. She was criticized for refusing to take part in a televised leaders' debate and for carefully controlling her campaign activities to keep the public at arm's length.

She was forced to apologize after she refused to acknowledge her party's battering in her initial post-election remarks.

The British media has been scathing of May. The Times newspaper ran a front-page story on May's tenuous future as Conservative leader Saturday with the headline "May stares into the abyss."

The Daily Mirror tabloid's cover read "Coalition of Crackpots," playing on the term "Coalition of Chaos" that May had used to describe the opposition parties. And the Sun tabloid led with "She's had her chips," pointing to a campaign moment of May awkwardly eating fries, while implying she was on the way out.