Boris Johnson has urged the public not to panic buy from UK supermarkets amid fears of a Christmas food shortage.
The prime minister’s official spokesman insisted there will be enough food in shops despite a French ban on UK freight lorries.
France has banned British hauliers for 48 hours in reaction to the emergence of a new strain of coronavirus in the UK.
Watch: Long queue at Marks & Spencer supermarket in Swansea
On Monday, there were long queues at a Morrisons supermarket in Whitley Bay, Tyne and Wear, a Waitrose in South Woodford, Essex, and at a Marks & Spencer Food Hall in Fforestfach, Swansea, Wales.
When asked if Johnson was telling people not to panic buy, his official spokesman said: “Yes, we’ve been clear throughout, we have resilient supply chains.
“It is the case that the majority of our food doesn’t come in through the short straits.
Watch: Shoppers queue at South Woodford branch of Waitrose in Essex
“It remains the position that people should shop normally, continue to be considerate in the way they shop.”
Earlier, transport secretary Grant Shapps had also urged calm, telling Sky News: “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.”
But Sainsbury’s warned that salad leaves, lettuce, cauliflowers, broccoli and citrus fruits could be missing from supermarket shelves “over the coming days” as a result of the ban.
However, it said Christmas dinner supplies are available and already in the UK.
A Sainsbury’s spokeswoman told Yahoo News UK: “We have good availability in our stores and encourage customers to shop as normal.”
A spokeswoman for Waitrose told Yahoo News UK: “We are working with our suppliers to understand the implications of today's decision by French authorities to suspend freight from the UK.
“The vast majority of our festive food is already within the UK - so we'll have what our customers need, however they are choosing to celebrate.”
Ian Wright, chief executive of the Food and Drink Federation, said there was no need to panic buy because of the haulage ban.
But he told BBC Breakfast on Monday there is “concern” around food supplies in the longer term, particularly after Christmas.
He said: “The problem is the return journey of drivers coming to the UK. If they cannot be guaranteed either that they will get out of the UK because of the congestion or that they will be able to secure a return journey full of whatever product it is, that’s going to make it much more unlikely for them to come in the first place.
“And, over time, because the transport system requires these round trips, that will reduce the ability of us to bring food into the country after Christmas if that takes effect.
“We need a pragmatic solution that gets drivers across the border and into the UK by whatever route in exactly the same way we had throughout the lockdown in March and in the earlier part of the year.”
Alex Veitch, general manager of trade group Logistics UK, told BBC Breakfast the ban is only affecting outbound freight with drivers in a truck, and that inbound goods are still moving.
“This is why we are saying at the current time, please, there is no need to panic buy, there are goods available in the shops, retailers are doing everything they can,” he said.
“But at the same time it is serious and we do need a resolution as quickly as possible.”
Andrew Opie, of the British Retail Consortium, said on Sunday: “The closure of France to UK traffic, including accompanied freight, poses difficulties for UK capacity to import and export key goods during the busy Christmas period.
“While goods can enter from France, few haulage firms will be willing to send trucks and drivers across to the UK without a guarantee they can return to the EU in a timely manner. This is a key supply route for fresh produce at this time of year: the Channel crossings see 10,000 trucks passing daily during peak periods such as in the run up to Christmas.
“We urge the UK government and the EU to find a pragmatic solution to this as soon as possible, to prevent disruption for consumers.
“Retailers have stocked up on goods ahead of Christmas which should prevent immediate problems.
“However, any prolonged closure of the French border would be a problem as the UK enters the final weeks before the transition ends on 31 December.”
Watch: Sainsbury’s warns of shortages over freight chaos