Chaos at ports caused by EU border closures has set back the UK's efforts to reassure foreign customers post-Brexit, the food industry has said.
Food and Drink Federation boss Ian Wright said UK exporters wanted to make sure foreign firms could rely on their supply chains after 1 January.
But the current crisis had harmed their cause, he told MPs.
"We've just proved... that you can't trust British products," he said. "And that's really unhelpful."
Mr Wright was giving evidence to an emergency hearing of the Commons business committee, called to examine the impact of the border delays on UK business and security of supply.
France shut its UK border for 48 hours on Sunday amid fears of a new coronavirus variant in the UK. More than 50 countries have now banned UK arrivals.
At the same time, UK-EU talks on a post-Brexit trade deal are continuing, with nine days left to reach and ratify any agreement.
Mr Wright said the current scenes at Dover, where the number of lorries stranded and unable to cross to France has continued to rise, could be "replicated at any point".
"I think we will see this happen particularly if we get a no-deal Brexit," he added.
Mr Wright said there were thought to be 4,000 trucks on their way to Dover at various points. He warned that the number could grow by the end of the day to possibly as high as 6,000 or 7,000.
He also criticised the government's handling of the announcement at the weekend and urged it to compensate those who had lost out.
The committee also heard that there were concerns over the welfare of lorry and van drivers caught up in the disruption, as the facilities provided for them are considered inadequate.
"We have no confidence, we have never had any confidence drivers will be looked after," said Duncan Buchanan of the Road Haulage Association.
"This is a very serious problem - whether you have moved trucks from one place to another, it is irrelevant."
Mr Buchanan said it was the start of supply chain disruption "of the like we have probably never experienced".
"Many of the retailers are saying that we are up until Christmas, we will be fine until Christmas at least, but we must recover very fast to keep the shops fully stocked after Christmas. It's a big worry," he added.
Andrew Opie, of the British Retail Consortium, agreed, saying that if lorries were not moving within 24 hours, there could be problems with the availability of fresh food products from 27 December.