Prime Minister Theresa May told European Union leaders on Friday she is confident a court ruling that could delay Britain's departure from the bloc will be overturned, and that she can stick to her Brexit timetable.
A spokesman said May had told German Chancellor Angela Merkel and European Commission President Jean-Claude Juncker she believed her case that the government, not parliament, should be responsible for triggering Article 50 of the EU's Lisbon Treaty and start the divorce would win in the country's highest court.
May is determined to carry out what she calls "the will of the people" and deliver Brexit, but a High Court ruling on Thursday that parliament must approve the process raised doubts over whether she can trigger Article 50 by the end of March as planned. It also prompted suggestions of an early election.
Her focus on ensuring government has the right to invoke Article 50 has incensed some lawmakers, and on Friday, a member of her ruling Conservative Party said he had resigned over "irreconcilable policy differences" with May.
"The focus of the government is on the Supreme Court case, winning that case and proceeding with article 50," May's spokesman told reporters.
"Clearly we are disappointed by yesterday's decision, we'd rather not be in this position but we are, so ... the key is our commitment to triggering Article 50 no later. The end of March remains the target for the government."
The spokesman declined to comment on whether the government was now drafting contingency plans for a possible failure in the Supreme Court, a move that would allow parliament to delay any move to start the divorce process.
"What is important here is that we had a referendum, there was an overwhelming result in favour of leaving the European Union and that is what the government must do," he said.
Parliament is unlikely to defy the referendum vote by blocking Brexit, but if - as one aide said was the logical conclusion of the court ruling - she is forced to draft legislation for both houses to consider, her March deadline looks tight, several lawmakers said.
That could force her to call an early election, they said, a move her aides have repeatedly rejected. Bookmakers odds on an election next year were cut after the court decision but 2020 was still the favourite date.
"ENEMIES OF THE PEOPLE"
The court ruling has spurred hope among investors and pro-EU lawmakers that parliament will now be able to put pressure on May's government - which has three high profile eurosceptic ministers in key roles - to soften any plans for a "hard Brexit", or a clean break with the EU's lucrative single market.
But it has enraged pro-Brexit campaigners and Britain's eurosceptic newspapers, with the Daily Mail calling the three judges who handed down the ruling "Enemies of the people".
The ruling is stirring passions in Britain just over four months after 52 percent of voters supported leaving the EU at a referendum which deepened splits in the country and gave voice to resentment - mirrored across Western Europe and the United States - with a ruling elite seen as out of touch.
Some lawmakers who had backed staying in the bloc were criticised on social media, accused of trying to stop Brexit.
"Tolerance must win over hate and scaremongering. I'm not alone in standing up for the 48 percent who also have the right to be heard and listened to," said Anna Soubry, a pro-EU lawmaker from May's ruling Conservative Party.
May had wanted to move on Brexit as quickly as possible - keen to show that although she campaigned quietly for Britain to remain in the EU she would "deliver" on the referendum.
There was clear frustration among her aides that the court had put a question mark over a schedule May has been outlining to EU leaders for weeks after some, especially French President Francois Hollande, called for Britain to move quickly.
She was due to "update" Hollande and European Council President Donald Tusk later on Friday, the spokesman said.
May, a former interior minister described as "intractable" by a former government official, has repeatedly said she does not want to give her hand away before launching some of the most complicated talks Britain has waged since World War Two.
Her tough stance seemed behind a decision by Conservative lawmaker Stephen Phillips, who backed Britain leaving the EU but wants parliament to have a say, to quit her party.
"It has become clear to me over the last few months that my growing and very significant policy differences with the current government mean that I am unable properly to represent the people who elected me," he said in a statement.
"This decision has been a difficult one."