Britain's finance minister has said that taxpayers' money should not be spent now on preparing for a "no deal" Brexit.
In a move that could anger Brexiteers who are reportedly calling for billions to be set aside in next month's budget, Chancellor of the Exchequer Philip Hammond said he would only spend the money "when it is responsible to do so".
Mr Hammond said planning for "no deal" was a "moving feast" because while extreme scenarios could be theoretically possible, they were highly unlikely in reality, such as air traffic coming to a halt.
His comments came after British Prime Minister Theresa May refused to say whether she would back Brexit if the referendum on leaving the European Union was held now.
Mrs May's de facto deputy Damian Green later suggested he would again back Remain if the EU referendum were held now, saying "I don't resile from my views".
Mr Hammond has reportedly faced calls from Brexit-backing ministers to do more to show the UK is ready to quit stalling Brexit negotiations in order to push the EU into talking about a future trade relationship.
European Council president Donald Tusk yesterday all but ruled out EU leaders giving the green light for trade talks at a crunch summit next week, as there has not been "sufficient progress" on withdrawal issues - a financial settlement, citizens rights and the border with Ireland.
Mr Hammond made clear the UK would be prepared for all outcomes, including leaving the EU with no deal, but stressed he would not commit money to that scenario now.
He said "we must be honest about the near-term challenges and complexities as we prepare to leave".
In an article for the Times newspaper, he went on: "As Chancellor of the Exchequer, it is my duty to be realistic about these challenges, and to carefully navigate the economy through this process in a way that protects our jobs, supports our businesses, underpins the prosperity of working families, and secures our public finances for decades to come.
"I also need to ensure that we are prepared for all outcomes, including a no-deal scenario.
"The government and the Treasury are prepared. We are planning for every outcome and we will find any necessary funding and we will only spend it when it's responsible to do so."
Mr Hammond also stressed the importance of avoiding a no-deal Brexit, as a lack of clarity about future trading terms is leading to business uncertainty and slowed investment.
"I believe the best stimulus we can provide for the economy right now, is certainty," he wrote.
"We will do that in two ways. First, by securing agreement on a time-limited implementation period - this is vital to give businesses and people the space to prepare for the future. Second, by reaching a deal on the terms of our future long-term relationship with the European Union."
His intervention may be interpreted as an attempt to fight back amid suggestions that pro-Brexit MPs want him ousted over his apparent support for a softer Brexit.
Mrs May has faced calls to reshuffle her cabinet following her mishap-strewn Conservative Party conference speech, which sparked a botched plot to oust her from Downing Street.
Other Tory MPs are thought to favour the sacking of Foreign Secretary Boris Johnson over weeks of perceived disloyalty over Brexit.
Asked on LBC yesterday if she was frustrated by Mr Johnson, Mrs May said "Boris is Foreign Secretary" and insisted he backed her plans for Brexit.
Mrs May has also received backing from Suella Fernandes, the chairman of the influential European Research Group of Brexit-backing Tories, over her repeated sidestepping of questions over how she would vote if the EU referendum was held now.
The PM, who backed Remain last year, insisted she was being "open and honest" when she could not give an answer.
Ms Fernandes told the Press Association: "The PM is entirely right to avoid being divisive.
"She is seeking to unite the country, not to perpetuate referendum divisions."
Asked by BBC Newsnight's Emily Maitlis if he thinks Britain would be better "if it remains", Mr Green replied: "It would have been but the public took their view.
"I'm a democrat, I believe that if people have spoken, it's the job of democratic politicians to do their best actually to put in place what people wanted."
Asked by the presenter if he could say "hand on heart Brexit was the right decision for the country", the First Secretary of State replied: "I argued against it but the country took the decision, I'm a democrat, I respect that decision."
The difficulties facing the Conservatives appear to provide ample material for Jeremy Corbyn to exploit at PMQs.
The Labour leader has already said it was "unacceptable" that Mrs May could not guarantee the status of either EU nationals in the UK or British expats on the continent in the event of a no-deal Brexit, during her LBC appearance.