Thomas O’Brien, the managing director of Boxer Gifts, which sells items such as toys and games, says he is likely to miss out on a million pounds because he will be unable to sell stock for the Christmas period that were ordered from overseas in September but has not arrived in time.
It comes as delays at UK ports ahead of the end of the Brexit transition period have been condemned as a "chaotic mess" by peers - though Mr O'Brien believes the coronavirus pandemic is primarily to blame for the issue.
UK importers are reported to be struggling with congestion problems at Felixstowe and Southampton and there are fears of major delays at Dover from the new year.
Mr O'Brien says that delays at ports such as Felixstowe originated because global demand plummeted as the coronavirus pandemic set in.
But he said that since May, a resurgence in shipping demand has meant that hold-ups have occurred and containers have consequently not arrived back at locations such as the Far East in time to be re-filled with the next round of orders to the UK.
Part of the issues is that shipments of personal protective equipment have been clogging ports, causing huge delays compounded by retailers and manufacturers importing goods for the Christmas shopping rush.
Customs checks with the European Union are expected to cause even more delays from January 1.
Speaking about one order, Mr O'Brien said: “It left China at the end of September and now they say it’s not going to arrive until after Christmas, which is unheard of. It’s 45 days generally.”
He estimated that 300,000 items of stock - much of it seasonally themed - ordered for Christmas sales has either not arrived or by now cannot be distributed to stores in time for Christmas, meaning his 20-strong business will lose around £1m in revenue.
In the House of Lords, Liberal Democrat Baroness Randerson said the Sevington lorry park, designed to relieve queues of around 7,000 lorries on Kent motorways, would not be ready until the end of February.
She said ministers had rejected a bid from the Dover port for funding for more passport checkpoints to reduce queues.
"The Government has had three years to prepare for Brexit," Lady Randerson said. "How have they got themselves into such a chaotic mess?"
Transport minister Baroness Vere of Norbiton said the Government was working closely with the freight sector on preparations for the end of the transition period.