Theresa May has dismissed speculation she could be ousted as prime minister over her Brexit agreement, saying: “I am going to see this through”.
Speaking in Downing Street, the prime minister said: “The course I have set out is the right one for our country and all our people.”
She vowed to get the deal signed off in Brussels and put it to a vote of MPs.
It follows a string of ministerial resignations and talk of a no confidence vote from Tory MPs.
Brexit Secretary Dominic Raab and Work and Pensions Secretary Esther McVey both quit earlier in protest at the withdrawal agreement, along with two junior ministers.
And leading backbench Brexiteer Jacob Rees-Mogg submitted a letter of no confidence in Mrs May to Sir Graham Brady, chairman of the Tories’ backbench 1922 Committee.
A vote will be triggered if 48 Tory MPs write letters to Sir Graham. It is understood 48 letters have not yet been received.
Mr Rees-Mogg told reporters that UK negotiating team had “given way on all the key points” adding: “The deal risks Brexit because it is not a proper Brexit.”
Mrs May spent nearly three hours fielding largely critical questions from MPs before holding a press conference in Downing Street to further answer her critics.
She acknowledged the agreement had entailed “difficult and sometimes uncomfortable decisions”.
“I understand fully that there are some who are unhappy with those compromises but this deal delivers what people voted for and it is in the national interest,” she said.
“We can only secure it, if we unite behind the agreement reached in cabinet yesterday.
“If we do not move forward with that agreement, nobody can know for sure the consequences that will follow.
“It will be to take a path of deep and grave uncertainty when the British people just want us to get on with it. They are looking to the Conservative Party to deliver.”
Asked if she would carry on as prime minister if she won a no-confidence vote by a single vote, Mrs May said: “Leadership is about taking the right decisions, not the easy ones.”
She said her job was to “bring back a deal that delivers on the vote of the British people”.
She added: “I believe this is a deal which does deliver that, which is in the national interest and am I going to see this through? Yes.”
Asked if she was struggling to fill the two cabinet posts vacated by Dominic Raab and Esther McVey earlier on Thursday, she joked: “I have had, actually, rather a busy day.”
A source told BBC political editor Laura Kuenssberg that Environment Secretary Michael Gove had been offered the job as Brexit Secretary and was understood to be considering it, but to be asking for assurances that he could pursue a different kind of deal.
Mrs May said Mr Gove was doing “an excellent job at Defra” adding: “I haven’t appointed a new Dexeu [Department for Exiting the European Union] secretary yet and I will be making appointments to the government in due course.”
By BBC Political Editor Laura Kuenssberg
The government, for today at least, is at the mercy of events not in control.
Theresa May’s vow to stay does not make her deep, deep problems disappear.
With her party in revolt, her colleagues departing – some determined to usher her out of office – we can’t, and don’t know yet, if Brexit can happen as planned, perhaps, if at all.
This could be a gale that’s weathered in a few days, or a serious storm that sweeps the government away.
Despite a warning from Tory backbencher Mark Francois earlier that it would be “mathematically impossible to get this deal through the House of Commons”, Mrs May said she believed, ultimately, her MPs would back it.
“I’m committed, as prime minister, to bringing the best deal back to the UK. I think MPs across my party who look at that deal will recognise the importance of delivering on the vote of the British people and recognise the importance of doing that in a way that does protect people’s jobs, protect security and protect the unity of our United Kingdom.”