Fresh food will run out, prices will rise and UK travellers will face border delays after a no-deal Brexit, civil servants are predicting.

Whitehall’s “reasonable worst case scenario” for crashing out of the EU is revealed by a government watchdog – one day before a promised Commons vote on ruling out the prospect.

The National Audit Office also reveals that £1.5bn is being spent by government on “urgent civil contingencies funding” in this financial year alone.

The projections are made as part of Operation Yellowhammer, the emergency planning project first disclosed when Philip Hammond was photographed with a secret Treasury document last autumn.

In its report, published ahead of Wednesday’s vote on vetoing no-deal if Theresa May’s Brexit deal is thrown out tonight, the NAO states: “Departments are working on the basis of a reasonable worst case scenario”, including:

* Delays at the border will mean significant reduction in flow of goods for up to six months.

* UK citizens will be subject to increased immigration checks at EU border posts.

* A reduction in choice and availability of certain fresh food supplies.

* The potential for price increases across utilities, food and fuel.

The chancellor admitted last year that ministers had been told to prepare to make cuts if there is a crash-out Brexit, after Operation Yellowhammer was made public.

They would have no choice but to “refocus government priorities”, amid Treasury warnings of a near-10 per cent hit to GDP blowing an £80bn-plus hole in the public finances.

Now the NAO report has set out the 12 “areas of risk” that Yellowhammer hopes to “mitigate and respond to” including; transport systems, people and goods crossing borders, healthcare, energy, law enforcement, national security and UK nationals in the EU.

It concludes that “most situations can be managed using existing legislation” – by setting aside fuel for “essential services” and allowing and relaxing hours-limits for lorry drivers.

But it points to emergency powers if necessary, saying: “If existing powers are insufficient, the next option would be to bring forward new legislation.”

These could be introduced if “an emergency has occurred, is occurring or is about to occur” or if necessary for “preventing, controlling or mitigating the emergency”.

Ms May promised the option to veto a no-deal two weeks ago, when faced with the resignations of several cabinet and junior ministers if she refused.