The head of a food and drink body said companies face a “black Christmas” due to delays at the French border.
Authorities announced journeys from the UK can resume, lifting a travel ban which had been imposed on Sunday over fears about the spread of a new, more infectious strain of coronavirus.
An agreement was made that those seeking to travel must have a negative Covid test result.
But “the deal will be far too late” for many delivering perishable produce, David Thomson, the chief executive of the Food and Drink Federation Scotland, said.
He told the BBC: “For those people who export fresh and perishable goods, particularly seafood and salmon in Scotland, it’s been an absolutely disastrous few days and it will lead to a black Christmas for those businesses.
“The deal will be far too late for many people who are delivering perishable goods to the continent.
“It’s too late now to get to customers before Christmas.”
Mr Thomson added: “We’ve heard of companies that are saying this is the final straw for them and that they will not be able to deal with the losses.
“People have to pay farmers and fishermen, people have to deal with the customers they’ve let down and they will not make the money that they would do in what is of course the most lucrative few days of the year for most food businesses in the lead-up to Christmas.
“Many, many businesses are going to have a very difficult few days trying to work out if they continue.”
Calls had already been made for perishable products, such as seafood and salmon, to be prioritised as lorry drivers begin moving freight across the Channel again.
James Withers, chief executive of Scotland Food and Drink, welcomed the travel ban being lifted as a “a first, positive step forward in 48 hours” and said: “In addition, UK Government told us it has a prioritisation process for perishable products (eg seafood) as part of the process of managing Kent lorry queues.
“Was planned for Brexit disruption in nine days time. If freight starts moving tomorrow, it must be activated.”
His statement was echoed by Scotland’s transport secretary Michael Matheson, who said: “The UK Government has informed us that they have a plan to deploy lateral flow tests to drivers at locations in Kent where drivers are parked, and UK ministers must now urgently prioritise those drivers with perishable goods, such as Scottish seafood and salmon.
“What has always been of concern is the impact on exporters, not least of Scotland’s premier food produce rightly in demand in Europe.
“This is their most critical time of year and the dismay caused by the uncertainty and length of delay has been avoidable and regrettable.”
Matheson said he had spoken to UK transport secretary Grant Shapps and been told that the UK Government agreed that the move will permit drivers and other essential travellers to travel to France within 72 hours of a clear test.