The cabinet has given the go-ahead for all of the UK’s no-deal Brexit planning to be implemented “in full” as the likelihood of dropping out out of the EU without any agreement increases.

Downing Street said the government’s priority was still to secure a deal, but that it had a duty to plan for every outcome and would now make a series of no-deal announcements in coming days.

Officials will now seek to communicate with six million British businesses, calling on them to enact their own contingency plans, and with private citizens on actions they should take. Whitehall officials will also implement proposals already publicised like those designed to ensure vital food and medical supplies do not run out.

But the fault lines running through the cabinet also became more defined with one senior minister said to have branded the idea of a no-deal Brexit a “unicorn” that Ms May’s top team should seek to “slay”, while a disagreement also broke out over whether so-called “indicative votes” would be needd to work out what approach can pass through parliament.

Some 3,500 troops will also be on stand-by to help deal with the impact of a no-deal Brexit if needed, it emerged.

It comes days after Ms May returned from a European Council summit in Brussels, where she failed to secure enough assurances to make her proposed withdrawal deal viable and with her plans still looking like they will be defeated when they are put to a Commons vote in the new year.

Announcing the plans to step up no-deal preparations, Theresa May’s official spokesman said: “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.

“This means we will now set in motion the remaining elements of our no-deal plans.”

He went on: “We have no deal plans and we will implement them in full.”

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

There was a clear warning to MPs in both the prime minister’s party and those sitting on opposition benches, that the best way of mitigating the chances of no deal is to back Ms May’s proposals when they are voted upon on January 14.

HMRC has already 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 relating to no-deal Brexit this week.

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 Theresa May’s spokesman

The government will also make available a 100-page “partnership pack” for all of the UK’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 will 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.

"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 Department of 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.

In the Commons, defence secretary Gavin Williamson said that while there had not been a “formal request” for support in no-deal Brexit planning, “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”.

Brexit Secretary Stephen Barclay said: “The government’s priority is to secure a deal – that hasn’t changed.

“But alongside that, as part of our continuation of preparing for no deal, a responsible government needs to ensure that we are ready for that default option – which we don’t want to happen – but we are ready in the event that it did happen.

“That’s why at cabinet today we agreed that preparing for no deal will be an operational priority within government, but our overall priority remains to secure a deal.”

MPs should vote on how to break brexit deadlock, says Greg Clark

The cabinet has been divided into different groups with some, such as international development secretary Penny Mordaunt pushing for a “managed no deal” Brexit, while others have threatened to resign if the government pulls the UK out without a deal.

Justice secretary David Gauke, among those who have threatened to quit, is said to have told colleagues: “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.”

The prime minister’s spokesman did not deny that a managed no deal scenario, and the idea of indicative votes were discussed by ministers. Brexit-backing Commons leader Andrea Leadsom has been a main critic of fellow ministers – including Amber Rudd and Greg Clark – who have suggested the votes could take place in the Commons to ascertain what options can be taken forward.

Tim Morris, chief executive of the UK Major Ports Group, welcomed the cabinet’s announcement of accelerated planning, saying: “Regardless of the politics we are 101 days away from Brexit, very close in business planning terms. It’s crucial that businesses have their contingency plans firmly in place.