Boris Johnson will hold crisis talks with senior ministers and officials after France banned hauliers carrying freight across the channel amid fears over the new coronavirus strain.
Countries around the world have banned flights from the UK as an emergency response to the emergence of the mutant coronavirus, which spreads more easily than previous strains.
Ahead of a meeting of the Cobra committee chaired by the Prime Minister, Transport Secretary Grant Shapps said emergency measures were being put in place to cope with a backlog of lorries heading for the channel ports.
But he sought to play down the potential impact, stressing that container freight was not hit by the French ban on travellers.
The markets tumbled in response to the escalating coronavirus crisis and the looming prospect of a no-deal Brexit at the end of the transition period on December 31.
More than £33 billion was wiped off the FTSE 100 within minutes of opening, as the index dropped more than 2%, although it later recovered to a fall of around 1.4%.
Along with France, countries across the world announced restrictions on UK travel following the disclosure that the highly infectious new strain is widespread across south-east England.
Italian authorities said the mutant strain had been detected in a traveller who recently returned to the country from the UK.
French health minister Olivier Veran said it was already "entirely possible" the new variant – VUI 202012/01 – was already circulating there, although tests had not detected it.
As well as affecting freight flows from Dover and the Channel Tunnel at Folkestone, the disruption will leave passengers stranded in the run-up to Christmas.
Mr Shapps attempted to calm fears about the wider impact of the French decision.
The Transport Secretary said hauliers were "quite used to anticipating disruption", adding there were variations in supply "all the time".
Mr Shapps said he was talking to French counterpart Jean-Baptiste Djebbari and told Sky News: "The absolute key is to get this resolved as soon as possible."
UPDATEOP STACK, M20, J8-J12 Coast bound.The M20 is now closed between J8-J12 Coast bound due to Operation Stack being implemented. @Port_of_Dover/@TruckShuttle/@LeShuttle are closed due to travel restrictions leaving the UK: https://t.co/omAnTp9wdJ#OpStack#OperationStackpic.twitter.com/gjBOUNjR2M
— KCC Highways (@KentHighways) December 21, 2020
Asked if consumers will see shortages in supermarkets, Mr Shapps said: "The supply chain is pretty robust in as much as you get variations in supply all the time. For the most part, people won't notice it."
He confirmed that the disused Manston Airport in Kent would be used as a lorry park, while Operation Stack – the contingency measures used to queue on the M20 whenever there is disruption at the channel – was already in place.
The Transport Secretary dismissed concerns about the impact of the travel ban on supplies of the Pfizer/BioNTech vaccine, which is manufactured in Belgium, because container freight was unaffected.
Following the French Government's announcement it will not accept any passengers arriving from the UK for the next 48hrs, we're asking the public & particularly hauliers not to travel to Kent ports or other routes to France.
We expect significant disruption in the area. 1/2
— Rt Hon Grant Shapps MP (@grantshapps) December 20, 2020
The chief executive of the Road Haulage Association (RHA), Richard Burnett, said the disruption could cause problems with "fresh food supply" in the run-up to Christmas.
He told BBC Radio 4's Today programme: "With it being so close to Christmas we're looking at 48 hours at this point in time in terms of the restrictions, we're likely to see Operation Stack building in terms of numbers of vehicles on the UK side and that might be a deterrent for EU hauliers to want to come so close to Christmas and end up being stranded here, that's part of the challenge that we're facing today."
Sainsbury's warned there could be "gaps over the coming days" in the supply of lettuce, some salad leaves, cauliflowers, broccoli and citrus fruit – all of which are imported from the continent at this time of year.
Today's stark figures are very worrying.
This will get worse before it gets better – but it will get better.
We all need to do our bit to keep the virus under control while we accelerate the vaccination programmehttps://t.co/Js3uGtYulX
— Matt Hancock (@MattHancock) December 20, 2020
Mr Johnson faced demands to recall Parliament to address the crisis, which follows the introduction of a new Tier 4 level of lockdown on London and large parts of south-east England.
Concerns about the spread of the new variant also led to the dramatic scaling back of Christmas plans, with mixing banned in Tier 4 and the three-household provision being allowed for just Christmas Day itself in the rest of England.
Conservative former minister Sir Desmond Swayne questioned the timing of the Government's announcements.
"They've been looking at it since September, and how convenient when Parliament went into recess on Thursday suddenly they were then able to produce this revelation," he told Today.
"Let's see the evidence then, let's have Parliament back and show us and convince us – come clean."
It's now imperative that PM seeks an agreement to extend the Brexit transition period. The new Covid strain – & the various implications of it – means we face a profoundly serious situation, & it demands our 100% attention. It would be unconscionable to compound it with Brexit.
— Nicola Sturgeon (@NicolaSturgeon) December 20, 2020
Scotland's First Minister Nicola Sturgeon said it was "imperative" the UK Government sought an extension to the Brexit transition period, which protects current trading arrangements with the EU until the end of the year.
Among the authorities imposing travel restrictions on passengers from the UK are: France, Ireland, the Netherlands, Belgium, Italy, Austria, Bulgaria, the Czech Republic, Slovakia, Denmark, El Salvador, Turkey, Canada and Hong Kong.
They reacted after Mr Johnson announced that the new variant was up to 70% more transmissible than the original strain while Health Secretary Matt Hancock admitted it was "out of control" and the Tier 4 lockdown may have to remain in place for months.
Concerns about the rapid spread of the disease were underlined with the publication of the latest official figures showing there had been a further 35,928 lab-confirmed cases of coronavirus in the UK as of 9am on Sunday.
And at an emergency meeting late on Sunday night, the Northern Ireland Executive agreed to reduce the five-day Christmas bubbling arrangements to just one day, following the rest of the UK.
Ministers also debated a temporary ban on travel from Great Britain to Northern Ireland because of the new Covid variant, with further discussions expected on Monday.