Thousands of troops have been put on standby to handle any fallout of Britain crashing out of the European Union without having secured a withdrawal deal.

The government has said that, with 100 days to go until Brexit day on 29 March, it will implement all of its no-deal planning “in full” – following a clash in cabinet reflected in the wider Tory Party.

Senior ministers went head-to-head, with one group demanding “no deal” become Britain’s central planning assumption, while others including the chancellor branded departing without an agreement a “unicorn” idea.

Jeremy Hunt, foreign secretary, is said to have told colleagues their party would never be forgiven if it fails to deliver Brexit, but other Conservatives vowed to do everything in their power to stop a no-deal scenario.

In yet another day of Brexit high drama, defence secretary Gavin Williamson revealed he had made 3,500 troops ready to “support any government department on any contingencies they may need”.

While he told MPs there had been no request for the troops yet, he said “What we are doing is putting contingency plans in place, and what we will do is have 3,500 service personnel held at readiness, including regulars and reserves, in order to support any government department on any contingencies they may need.”

The Ministry of Defence later confirmed the troops would be put on alert in addition to the 5,000 already on standby to deal with potential terror attacks.

The troops announcement came after Theresa May chaired a cabinet which eventually decided to push the button on all of the government’s advanced no-deal plans – but only after a heated discussion over what the ramping up of preparations means.

Brexit and Travel: Everything you need to know with 100 days to go

Downing Street insisted afterwards that the “top priority” was still securing support for Ms May‘s deal, but details of the crunch meeting that later emerged underlined ongoing divisions at the top of government .

Mr Hunt said that if the Conservative Party fails to deliver Brexit then the issue will become as electorally toxic as the Liberal Democrat’s failure to hold down tuition fees.

Managed no deal is not an option and it’s not on offer from the EU. The responsibility of cabinet ministers is not to propagate unicorns but to slay them Justice secretary David Gauke

He slammed colleagues for fanning the flames of speculation around a second referendum, which he claimed had led to a lack of willingness in Brussels to offer further concessions.

Home secretary Sajid Javid and chief secretary to the Treasury Liz Truss were among those wanting no deal to become the central assumption of government planning.

But Philip Hammond made clear the decision to accelerate plans must be viewed as a precaution, rather than a policy shift – branding the “managed no-deal” approach advocated by the likes of aid secretary Penny Mordaunt as a “unicorn” idea.

Justice secretary David Gauke piled in, telling colleagues: “Managed no deal is not an option and it’s not on offer from the EU.

"Brexit betrayal" march in London Show all 43 1 /43 "Brexit betrayal" march in London "Brexit betrayal" march in London A protester holds an anti-BBC sign Angela Christofilou/The Independent "Brexit betrayal" march in London A pro-brexit demonstrator holds a sign in the picket line Angela Christofilou/The Independent "Brexit betrayal" march in London A protester carrying a noose at the "Brexit betrayal" march. The man carrying it told a reporter: "That's what the traitor May deserves." 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in reference to the annual World Economic Forum meeting in Davos Angela Christofilou/The Independent "Brexit betrayal" march in London A protester holds a pro-brexit sign on the march Angela Christofilou/The Independent "Brexit betrayal" march in London The march approaches parliament Angela Christofilou/The Independent "Brexit betrayal" march in London A protester distributes pro-brexit lapel badges Angela Christofilou/The Independent "Brexit betrayal" march in London A demonstrator wears an anti-EU poster and holds an anti-BBC sign Angela Christofilou/The Independent "Brexit betrayal" march in London A smoke bomb is deployed in Parliament Square as the march comes across the counter-demonstration Angela Christofilou/The Independent "Brexit betrayal" march in London Angela Christofilou/The Independent "Brexit betrayal" march in London A flag bearing the Arms of Plantagenet flies in theprot Angela Christofilou/The Independent "Brexit betrayal" march in London Protesters on the Brexit 'betrayal' march in London on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Protesters on the Brexit 'betrayal' march in London on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Brexit 'betrayal' marchers gathering on Park Lane ahead of a protest on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Brexit 'betrayal' marchers gathering on Park Lane ahead of a protest on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Angela Christofilou/The Independent

“The responsibility of cabinet ministers is not to propagate unicorns but to slay them.”

Pensions secretary Amber Rudd said the UK would only have a bright future after Brexit if the country had a deal, and urged her colleagues to think about job losses in their constituencies if no deal comes to pass.

Of the decision to trigger advanced preparations, she said: “Just because you put a seat belt on [it] doesn’t mean you should crash the car.”

The Independent understands the idea of holding an “indicative vote” in the Commons, to see what kind of Brexit outcome is passable, was rejected by more people than those who supported it – with backers still including Ms Rudd and education secretary Damian Hinds.

But Northern Ireland secretary Karen Bradley, a close ally of the prime minister, withheld her support and suggested that the prospect of the idea was fading.

Brexit secretary Stephen Barclay: UK is readying businesses for no-deal scerario

HMRC contacted around 150,000 exporters last week to notify them about changes to customs arrangements, with officials set to email a further 80,000 key businesses and business groups this week.

The government will also make available a 100 page “partnership pack” for all of Britain’s firms, setting out measures that should be taken in relation to customs, VAT and regulatory changes.

Ministers have already announced plans to stockpile food and medicines, chartering ferries to bring in extra supplies and providing extra resources for border agencies. Downing Street said that advice on no-deal preparations would also be going out to households by various channels over the coming weeks.

The Treasury will supply an additional £2bn on top of the £2bn already provided, with the Home Office receiving £500m for border security and handling the settlement scheme for EU nationals who want to remain in the country.

Another £400m will go to Defra, the environment department, for projects including ensuring clean drinking water, which the UK treats with chemicals and gases imported from the EU.

Theresa May confirms date for meaningful vote on Brexit deal for 2019

The Department for International Trade, which would need to accelerate efforts to replicate dozens of agreements between the EU and countries such as Japan, Mexico and South Korea, is expected to receive around £130m to recruit more trade negotiators.

Ms May returned from a European Council summit in Brussels, where she failed to secure enough assurances to make her proposed withdrawal deal viable. Her plan still looks like it will be defeated when put to a Commons vote in the new year.

Announcing the effort to step up no-deal preparations, Ms May’s spokesperson said she still believes she could win changes to the deal.

He added: “Cabinet agreed that, with just over three months until we exit from the European Union, we have now reached the point where we need to ramp up these preparations.”

Jenny Chapman MP, Labour’s shadow Brexit minister, said the move “is testament to the prime minister’s failure” in negotiations, which would now cost the government billions of pounds of taxpayers’ money.

She said: “A no-deal Brexit would be a disaster for jobs, the economy and the border in Northern Ireland. It is simply not a viable option.