Royal Navy vessels have been deployed to “threats of illegal fishing” in UK waters as part of no-deal Brexit preparations, the UK Government has confirmed.

An exercise has taken place that was part of “live” planning in the event of no deal being reached with the EU.

Government officials have revealed there is a playbook in Whitehall that “maps out every single foreseeable scenario” after December 31 – and lists minister-approved responses to allow for immediate remedy.

The news comes after the Ministry of Defence said that four 80-metre gunboats were now on standby to guard British waters from EU trawlers in the event that there is no new agreement on fishing rights after December 31, when transitional arrangements end.

Reports have suggested ministers are preparing to boost Navy powers to allow them to board European vessels and arrest fishermen breaking post-Brexit rules as part of a cranking up of preparations for a no deal.

A Government spokesman said: “We’ve run live exercises moving fresh produce and fish across the border, and scrambled naval vessels to respond to threats of illegal fishing in our soon-to-be sovereign waters.”

The XO Committee dealing with Brexit preparations is said to have met more than 200 times so far.

It is planning to meet “well into the New Year”, according to the Cabinet Office, as ministers look to assure the public the country is ready for 2021 regardless of whether there is a trade deal with the European Union.

Both sides have been downbeat over the prospect of an agreement.

The Prime Minister Boris Johnson and European Commission president Ursula von der Leyen have set Sunday as the deadline for making a firm decision on the talks.

The XO, which is chaired by the Chancellor of the Duchy of Lancaster Michael Gove, wants to increase public awareness about the changing rules that are set to come into force in a little under three weeks.

“As with any major change, deal or no deal, there will be challenges and bumps to overcome,” said a Government spokesman.

“There will be new rules for those travelling and traders, this would be the case with a free trade agreement – just as it would without one.

“We’ve chosen to stage the introduction of our new border requirements – but the EU has not.

“That is why businesses need to be ready for the new requirements on January 1 no matter the outcome – or risk goods not passing through the borders and adding to queues.”

The spokesman said several measures would help ensure the country can keep moving once the transitional arrangement with Brussels ends.

These include additional border staff – with 900 hired and 1,100 more to be recruited by March – along with seven inland inspection sites, a round-the-clock Border Operations Centre, support phone lines and a hauliers’ app.

“Having safeguarded the flow of critical goods, such as vaccines and vital medicines, through surging freight capacity, no one needs to worry about our food, medicine or vital supply chains,” said the Government spokesman.