There will be higher prices and empty supermarket shelves.

Key points: Major food chains sign a letter flagging concerns about disruptions to food security

Major food chains sign a letter flagging concerns about disruptions to food security They're warning the fresh supply chain will be disrupted in the event of a no-deal scenario

They're warning the fresh supply chain will be disrupted in the event of a no-deal scenario British military bases abroad are reportedly stockpiling food and fuel in case the deal falls through

It is a simple warning to focus the minds of politicians and those they lead in the midst of a British winter.

With just 60 days until Brexit, the UK's biggest and most powerful food retailers have warned Members of Parliament that leaving the European Union without a deal on March 29 would threaten food security.

The chief executives of supermarket chains Sainsbury's, Asda and Waitrose, retail group Marks and Spencer as well as fast food giants McDonald's and KFC are among the 12 signatories on the letter from the British Retail Consortium (BRC).

They warn the "just-in-time" or fresh supply chain will be significantly disrupted in the event of a no-deal scenario.

"Government data suggests freight trade between Calais and Dover may reduce by 87 per cent against current levels as a result," states the letter, which was addressed to the House of Commons.

"For consumers, this will reduce the availability and shelf life of many products in our stores."

Hard Brexiteers, who have long argued the UK should leave the EU regardless of a deal, will no doubt declare it a case of scaremongering.

But how can they be so sure?

Retailers and everyday preppers have already begun stockpiling in the UK but, as the letter also notes, available warehouses have already been filled and "even if there were more space it is impossible to stockpile fresh produce".

The BRC says that in March the UK gets 90 per cent of its lettuces, 80 per cent of its tomatoes and 70 per cent of its soft fruit from the EU — all perishable produce that needs to be moved quickly from farm to store.

It is a stark message that the fresh, unprocessed food on dinner plates around the nation is not a given but a delight that could be taken away by Brexit.

And a no-deal Brexit is certainly a live option.

Supermarket chains say the fresh supply chain will be disrupted in the event of a no-deal scenario. ( ABC News: Dan Loh )

Theresa May's negotiated Brexit deal suffered the massive and rather humiliating defeat in the House of Commons on January 15 — she then came back to the Parliament with a plan B, which was exactly the same as her plan A.

On Tuesday evening UK time, the British Parliament will embark on yet another key round of votes to try to untangle the shambles that is Brexit.

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It is not another meaningful vote on the Brexit deal done with Brussels, but a chance for MPs to try to get the process back on track via amendments.

Politicians from across party lines have put forward dozens of amendments to try to break the logjam, but Speaker John Bercow will choose only a few to be debated.

One from powerful backbencher Sir Graham Brady is likely to get up.

It calls for an alternative arrangement to the so-called Irish backstop, to avoid a hard border between Northern Ireland and the Republic of Ireland.

Another from Labour MP Yvette Cooper would delay the Brexit date by three to six months, beyond the March 29 deadline.

If either is successful, the Prime Minister can go back to Brussels and seek more ground. If the leaders of the 27 bloc nations won't play ball, she has nothing more than she started with.

That will mean no-deal is more likely.

"We are extremely concerned that our customers will be among the first to experience the realities of a no-deal Brexit," the BRC letter states.

Retailers are not the only ones concerned. It has been reported that British military bases abroad have been stockpiling food, fuel, spare parts and ammunition in anticipation of a no-deal scenario.

The Queen has even dipped her toe in, using a speech to a women's institute last week to call for people to come together "to seek out the common ground" and to never lose "sight of the bigger picture" — widely seen as thinly veiled reference to the Brexit debate.

The biggest threat may not come from the lack of apples, but the anger that comes from the populous unable to source the fruit and vegetables they are used to.

On the weekend Health Secretary Matt Hancock refused to rule out martial law if a no-deal Brexit led to civil disobedience over shortages of essential items, saying the Government was looking at all options.

That's right — troops on London streets to maintain calm if bare supermarkets shelves lead to unrest.