Several big ports, including Felixstowe - the UK’s biggest container port - and Southampton are so congested some container ships are skipping the UK and taking their cargo straight to Rotterdam.
Toys are among the goods being held up in the clogged ports with the industry body warning stock could run low in the crucial Christmas period, while prices could quadruple.
White goods, homeware and building supplies are also reportedly affected by the disruption.
The situation was compounded by PPE (personal protective equipment) brought in to supply key workers during the coronavirus pandemic not being collected from ports.
There has also been an uptick in imports as retailers stock up ahead of the end of the Brexit transition period on December 31.
Such is the scale of the problem, some container ships are refusing to collect empty containers or exports after dropping off goods in the UK because they do not want to miss slots at other ports such as Rotterdam, Antwerp or Hamburg - what is known as a "cut and run".
Eleanor Hadland, ports analyst at maritime consultancy Drewry, said she had "never known it like it".
Ms Hadland said: “They’re leaving cargo in the yard, so the yard gets even busier, which slows down deliveries at the gate, which slows down the next ship, so that ship cuts and runs and leaves more cargo in the yard.
“Unless you turn off the tap – so stop ships coming – you can’t clear the backlog.”
“It’s pretty much the worse it’s been in a long while,” Ms Hadland said.
“I’ve never known it like it. I’ve been in the sector 25 years.”
Ms Hadland said disruption has built up since August due to a combination of factors, including a “massive upswing in imports” following the end of the first coronavirus lockdown due to pent-up demand and stockpiling by importers concerned about the impact of a second wave of the virus.
The British Toy and Hobby Association said it is aware of companies suffering “serious issues” retrieving their stock from ports in Felixstowe and Southampton.
Its statement continued: “Toy manufacturers are facing a drastic price increase on freight due to a shortage of capacity and containers, which has seen prices increase three-fold and as much as four-fold in some cases.
“Vessels have been diverted to Rotterdam due to congestion at Felixstowe and will now miss the Christmas season.
“This is troubling for the toy industry who are under pressure to ensure children around the country get to open their exciting new toys on Christmas Day and into the new year.”
Derek Crookes, of the Toy Retailers Association, advised Christmas shoppers to “get out there and try and get any products that they want as they may well run out”.
Culture secretary Oliver Dowden said he was still "very hopeful" the UK could get a Canada-style deal with the European Union despite prime minister Boris Johnson telling the public and businesses to prepare for an Australian-style option - which means leaving on WTO terms - on January 1. "What we are aiming for, and we have been aiming for all the way through and will continue to work towards is a Canada style free trade relationship," he told Good Morning Britain's Ben Shephard and Charlotte Hawkins. Asked to clarify whether it was "Australia or Canadian", Mr Dowden said the government were aiming for a "so-called Canada style free trade agreement" but Westminster would "not accept it at any price".
On Wednesday, the Department for Transport eased restrictions on drivers’ working hours in a bid to ease the backlog at ports.
Unite national officer for road haulage Adrian Jones said drivers are being “forced to pay for the mismanagement of others”.
He went on: “Relaxing driving hours increases fatigue, which increases the risk of accident for the drivers themselves and all other road users.”