Two ministers touted as a potential caretaker prime minister in reports of a cabinet coup say they fully back Theresa May.
Newspapers claim cabinet ministers are plotting a coup against the prime minister, aiming to replace her with a caretaker leader until a proper leadership contest is held later in the year.
Environment Secretary Michael Gove told reporters it was "not the time to change the captain of the ship", and Mrs May's de facto deputy David Lidington insisted he was "100% behind" Mrs May.
The Sunday Times had reported that Mr Lidington, who voted Remain, was being lined up, while the Mail on Sunday said the Brexiteer Mr Gove was the "consensus choice".
Mrs May has been holding talks with colleagues and senior Brexiteers, including Boris Johnson, at Chequers, her country retreat.
The prime minister has come under growing pressure to quit following a week in which she was forced to ask the EU for an extension to Article 50, and criticised for blaming the delay to Brexit on MPs.
The withdrawal deal she has negotiated with the EU has been overwhelmingly rejected in the Commons twice, and it remains unclear whether she will bring it back a third time next week after she wrote to MPs saying she would only do so if there was "sufficient support".
One senior backbencher told the BBC's Iain Watson that even standing aside would not be enough for her deal to be voted through, and that Mrs May might as well "dig in".
Brexit Secretary Stephen Barclay said an election would become more likely if MPs voted this week for a Brexit option the government did not want.
MPs are expected to get the chance to hold a series of so-called indicative votes on possible alternatives to Mrs May's withdrawal deal, but Mr Barclay said they would "not be binding".
On Saturday, hundreds of thousands of people marched in central London to call for another EU referendum.
Organisers said the initial count showed more than a million people had turned up - putting it on a par with the biggest march of the century, the Stop the War march in 2003.
Lidington v Gove
MP for Aylesbury since 1992 and now Cabinet Office Minister, David Lidington, below left, is the prime minister's right-hand man and behind-the-scenes fixer.
Once private secretary to William Hague when he was Tory leader, Mr Lidington was the longest-serving Minister for Europe under David Cameron and is clearly from the Remain camp. That makes him an unacceptable replacement for Theresa May in the eyes of Brexiteers.
Lidington is well-liked among fellow MPs and has an easy way with journalists, but he has attracted criticism from some quarters for his voting record, especially on LGBTQ rights. He voted against same sex marriage and to maintain a ban on the promotion of homosexuality in schools.
Former journalist turned MP for Surrey Heath, Michael Gove, above right, is currently environment secretary. He's previously held the justice and education briefs.
He and Boris Johnson helped lead Vote Leave to victory in the EU referendum, but Gove later ran against his former Brexit ally for the Tory leadership. He was subsequently sacked as a minister by Theresa May when she eventually won that contest.
Now having worked his way back into the senior echelons of government, Mr Gove is seen as someone who could hold the Conservative Party together, and might be a candidate Remainers could stomach because he's hinted he could be open to a softer form of Brexit. Arch Brexiteers feel, though, that for that very reason he'd be an unacceptable choice.
Parliament to hold 'indicative' votes
The leadership row comes ahead of a week where the PM is expected to lose further control over the Brexit process.
In the coming days, as many as six other options, in addition to Mrs May's deal, could be put to indicative votes in order to see which are most popular. They are:
- Revoking Article 50 and cancelling Brexit
- Another referendum
- The PM's deal plus a customs union
- The PM's deal plus both a customs union and single market access
- A Canada-style free trade agreement
- Leaving the EU without a deal
Mr Hammond said he would remove revoking Article 50 and a no-deal Brexit from the list, as "both of those would have very serious and negative consequences for our country".
On the subject of a second referendum, he said: "It is a coherent proposition and deserves to be considered, along with the other proposals."
But Mr Barclay said there was a "crisis" because "Parliament is trying to take over the government".
He said if MPs vote for a Brexit outcome at odds with the Tory manifesto - for example, in favour of maintaining single market membership - "the risk of a general election increases, because you potentially have a situation where Parliament is instructing the executive to do something that is counter to what it was elected to do".
Shadow Brexit secretary Keir Starmer said the indicative votes must be a "serious exercise".
He said Labour would go into the process "in good faith" but there needed to be "assurance that the prime minister isn't going to use it just to frustrate the process".
Labour chairman of the Brexit scrutiny committee Hilary Benn told Sky News MPs were just doing their job by attempting to take control of the process.