- Video report by ITV News Political Correspondent Paul Brand
Theresa May has denied ever considering quitting as Prime Minister, despite a "tough week" that saw her lose key Cabinet members including former Brexit secretary Dominic Raab.
Mrs May said "of course it has been a tough week" but suggested a change of leadership would bring in "a degree of uncertainty" and a "risk that Brexit gets delayed or frustrated."
She claimed negotiations were "always going to get even more difficult right toward the end" and said the next seven days "are going to be critical" as she travels to Brussels to talk to figures including Jean-Claude Juncker, the European Commission President.
The Prime Minister was speaking on Sky News' Sophy Ridge on Sunday programme after Mr Raab accused her in a newspaper article of failing to stand up to a bullying European Union, saying she should be prepared to "walk away" from negotiations.
Mrs May later revealed that she had spoken to Sir Graham Brady, who chairs the powerful backbench 1922 Committee, and as far as she was aware the required number of Tory MPs' letters to trigger a no confidence vote in her had not been reached.
Asked if the 48 letter threshold had been reached she added: "As far as I know, no, the answer to your question is no."
- ITV News Correspondent Angus Walker on the political reaction in Brussels
Despite widespread criticism of the deal, leader of the Labour Party, Jeremy Corbyn, decided against calling for a second referendum, saying it was "an option for the future" and "not an option for today".
Also speaking to Ms Ridge, Mr Corbyn added that his party "couldn't stop" Brexit because of parliamentary arithmetic.
Asked if he would support Remain in a second referendum, he said: "I don't know how I am going to vote, what the options would be at that time."
Meanwhile on The Andrew Marr Show, shadow attorney general Baroness Shami Chakrabarti, disagreed with her party leader, saying that "theoretically" Brexit could be stopped, but added the current situation is "a long way from that".
The 49-year-old added that Mrs May's Brexit deal is "unacceptable" in its current form and does not meet Labour's six Brexit tests, meaning she would not vote for it, nor would she encourage other Labour members too.
However, Baroness Chakrabarti continued that if the Prime Minister "acted now", she could renegotiate a better deal.
Mr Raab, who stepped down as Brexit secretary on Thursday, saying he could not accept the terms of the deal done by the Prime Minister, told the Sunday Times the UK should demand an agreement that allows it to unilaterally leave any customs union.
Later appearing on The Andrew Marr Show, Mr Raab described the deal as "fatally flawed", but said it could be remedied by just "two or three points" being changed, but that "it is very late in the day now" for more negotiations to take place.
The 44-year-old said he took issue with the customs backstop plan which he believes will mean the UK would remain tied to the EU with no say and no way of independently freeing itself, while Northern Ireland would be treated as a "third country".
Mr Raab said: "The argument is made 'let's get this over the line and play for the second half, the future relationship negotiations'.
"But... it would tilt the advantage in favour of the EU and prejudice, frankly taint, the second phase of negotiation.
"So I think it is a fatal flaw and the shame of it is I have supported this PM all the way through her premiership - I still do now.
"We were close to a deal and actually if these two or three points were changed I still think a deal could be done but it is very late in the day now and we need to change course."
He spoke after two opinion polls suggested the week of chaos in Westminster has badly dented the Conservatives’ election fortunes, with the Tories now trailing Jeremy Corbyn’s Labour.
Amid ongoing talk of a plot to replace Mrs May through a confidence vote, one of her ministers said there is still time for “more to be done” on the Brexit deal, despite an EU summit scheduled for November 25 to confirm it.
Andrea Leadsom, the Brexiteer Commons’ leader who is believed to have held talks with four other Cabinet ministers on how Mrs May's Brexit deal could be tweaked, said she supports the Prime Minister but suggested there is an opportunity before the special European Council meeting to get “the best possible deal for the UK”.
On both Marr and in the Sunday Times, Mr Raab accused the EU of "blackmail" and "bullying", but accused the Government of lacking political will during negotiations.
Speaking on the BBC One show, the Tory MP said: "I do think we are being bullied, I do think we are being subjected to what is pretty close to blackmail frankly.
"I do think there is a point at which, we probably should have done it before, were we just say 'I'm sorry this is the United Kingdom of Great Britain and Northern Ireland, we cannot accept those dictated terms'."
Asked if he believed the deal was worth the "£39 billion "divorce bill", Mr Raab gave a simple "no".
At the end of a bruising week for the Prime Minister, she used an interview with the Daily Mail on Saturday to tell her critics their alternative plans for Brexit would not solve the main problem – the North Ireland/Ireland border backstop arrangement.
She told the newspaper: “People say ‘if you could only just do something slightly different, have a Norway model or a Canada model, this backstop issue would go away’. It would not. That issue is still going to be there.
“Some politicians get so embroiled in the intricacies of their argument they forget it is not about this theory or that theory, or does it make me look good.”
Last week saw the departure of Mr Raab and work and pensions secretary Esther McVey, plus the launch of a high-profile insurrection on the backbenches to remove Mrs May from office.
She responded by bringing former home secretary Amber Rudd, who quit over the Windrush scandal, back into Cabinet to replace Ms McVey.
Steve Barclay took over as Brexit Secretary but with a reduced role.
Meanwhile Zac Goldsmith, the Richmond MP and failed Tory London mayoral candidate in 2016, revealed he has joined those who have sent a letter of no confidence in Mrs May to Sir Graham Brady, chairman of the 1922 committee of backbench MPs.
Writing in the Sunday Telegraph, Mr Goldsmith said that under the PM’s plan “in effect, Britain would remain in the EU, but without having any say”.
He added: “Had that been the choice, I personally would have voted to Remain.
“The withdrawal agreement we have been presented with is unacceptable to Leave and Remain voters alike.
“It has close to zero chance of making it through Parliament and with only five months remaining, we cannot afford to waste any more time on it.”
While the number of letters that Sir Graham has received is not known, the MP for Altrincham and Sale West said it is not yet at 48 and that some MPs who claim to have submitted letters are lying.
In an interview with the Mail on Sunday, Ms Rudd blasted attempts to force a no-confidence vote, warning it could make the Government “look a little unhinged”.
“I hope they go back into their corners and we can get on with doing what we’re expected to do, which is delivering a Brexit I hope will protect the economy,” she said.
“They might have gone off a little early because it feels to me they’re rowing back.
“What could be madder at this stage, with seven days to go [to the Brussels summit] to undermine the Prime Minister. Such a mistake.”
In a sign the Tory civil war over Brexit is not calming, Middle East minister Alistair Burt warned rebels the “consensus” that pro-EU MPs should reluctantly respect the 2016 referendum result could break down if she is toppled.
Mr Burt, whose role spans the Foreign Office and Department for International Development, attacked a tweet by Steve Baker, deputy chairman of the European Research Group, in which the latter promoted a lawyer’s legal case against the agreement reached with Brussels.
Mr Burt wrote: “Be very clear. If an agreed deal on leaving between the Govt and the EU is voted down by purist Brexiteers, do not be surprised if consensus on accepting the result of the referendum by Remain voting MPs breaks down.
“Parliament will not support no deal.”
Ambassadors from the EU 27 will meet in Brussels on Sunday to be briefed on the deal by Michel Barnier, the EU's chief Brexit negotiator.