With two days to go until the crucial Brexit vote, the prime minister has warned MPs they face "uncharted waters" if they reject her deal.
Speaking to the Mail on Sunday, the PM said a rejection of her proposals would mean "grave uncertainty" for the UK.
She warned MPs their actions could lead to a general election, and there was a "very real risk of no Brexit".
Downing Street has also denied newspaper reports that Theresa May will postpone Tuesday's vote.
"The vote is going ahead," a spokesman said.
Last month, the UK agreed a Brexit deal with the EU - but it still needs to be approved by Parliament.
Labour, the Liberal Democrats, the DUP, and dozens of Conservative MPs have said they cannot support the deal, meaning it is unlikely to pass.
If the deal is rejected, it is unclear what happens next - with Mrs May insisting her deal was best for the country.
On Sunday, English Defence League founder Tommy Robinson is to join a pro-Brexit march in London, organised by UKIP.
A counter-protest against "far-right extremists" is being organised to take place at the same time, with anti-fascist groups and Labour-backed campaigners taking part.