Troops will be deployed across the country to help with preparations for a no-deal Brexit, the government has announced.

Ministers have issued a formal notice calling up British army reservists to help tackle the impact of crashing out of the EU “on the welfare, health and security of UK citizens and economic stability of the UK”.

The Ministry of Defence said it was supporting no-deal preparations across government to ensure there are “effective and proportionate contingency plans in place”.

Gavin Williamson, the defence secretary, told MPs last month that 3,500 troops are on standby to help with no-deal planning.

Around 350 of these are now being called up and deployed.

In a parliamentary statement, defence minister Mark Lancaster said: “A new order has been made under section 56(1B) of the Reserve Forces Act 1996 to enable reservists to be called into permanent service in support of the [government’s] contingency planning for a no-deal EU exit scenario.

“Defence is committed to assisting the cabinet office coordinated work programme to ensure that there are effective and proportionate contingency plans in place to mitigate the potential immediate impacts leaving the EU, under a no-deal scenario, might have on the welfare, health and security of UK citizens and economic stability of the UK.”

He said the troops would perform a range of tasks, including reinforcing existing army operations, liaising with other authorities and providing specialist skills. They will also be sent to help at regional command centres and tasked with implementing no-deal preparations being carried out by other government departments.

The troops will initially be deployed for one year, starting from 10 February.

Labour MP Ian Murray, a supporter of the Best for Britain campaign for another referendum, said: “Calling up the reserves shows just how serious the threat of a no-deal Brexit is.

“It is staggering that soldiers are being put on standby because of the risk of a constitutional crisis of the government’s own making. A no-deal scenario should be ruled out immediately by the prime minister, to avoid this chaos. There is absolutely no parliamentary support for this.”

Last month, Mr Williamson told MPs: “What 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 latest move underlines the government’s refusal to rule out leaving the EU without a deal, after Theresa May’s proposed withdrawal agreement was overwhelmingly rejected by parliament.

The prime minister has announced plans for cross-party talks to try to find an outcome that MPs can support, but has dismissed Jeremy Corbyn’s demand that she rule out no deal as an option before discussions begin.

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Delivering a speech in Hastings, Mr Corbyn said: “The prime minister seems completely unable to grasp what has actually happened.

“She seems to be prepared to send the country hurtling towards a cliff edge.

“To get a deal that can command a majority in parliament, Theresa May has to ditch the red lines and get serious about proposals for the future.”

And in a letter to Ms May, he added: “We are firmly of the opinion that the starting point for any talks about how to break the Brexit deadlock must be that the threat of a disastrous no-deal outcome is ruled out.

“I note that it is a position shared by all the opposition parties, including the DUP, and is the expressed will of parliament. If you are serious about reaching a deal, then no deal must be ruled out.