All pork products made in the Irish Republic since September have been recalled over fears they are contaminated with a toxic substance.
The action was taken after dioxins were found in slaughtered pigs thought to have eaten contaminated feed.
Tests showed some pork products contained up to 200 times more dioxins than the recognised safety limit.
The UK's Food Standards Agency said it did not believe at this stage that UK consumers faced any "significant risk".
Food safety expert Professor Hugh Pennington told the BBC the health risk was "very, very low".
He said: "You have to have a lot of these compounds. You have to eat a lot of them, enormous amounts to have any visible effect."
But consumers and retailers in the Irish Republic have been warned to destroy all Irish pork and bacon products bought since 1 September as a precaution.
Bacon, ham, sausages, white pudding and pizzas with ham toppings are also included in the withdrawal of stocks.
A spokesman for discount supermarket Lidl said half of its stores had removed "own-brand" black pudding and pork belly products sourced from the Irish Republic from their shelves.
He added that half of Lidl's stores had stocked these products and refunds are being offered to people who had bought the products.
Waitrose said all of its fresh pork was British so it was unaffected.
Other supermarkets, including Tesco, contacted by BBC News said they were continuing to check their supplies but many believed they did not stock pork products imported from the Republic of Ireland.
Dioxins are formed during combustion processes, such as waste incineration, and during some industrial processes.
Suspicions over contamination were first raised on Monday as a result of the routine testing of pigs, which indicated the presence of polychlorinated biphenyls (PCBs) - banned in the Irish Republic since the 1970s - in animal feed.
Restrictions were placed on a number of pig farms and tests on pork samples confirmed the presence of dioxins on Saturday afternoon.
Chronic long-term exposure to dioxins can have serious health effects, including causing cancers, but Irish officials said the recall would ensure consumers only had minimum exposure to it.
The country's chief medical officer, Dr Tony Holohan, said anyone who had eaten pig meat did not need to seek medical help.
An Irish government spokeswoman said: "Investigations involving the Department of Agriculture, Fisheries and Food (DAFF) and the Food Safety Authority of Ireland are continuing to determine the extent of the contamination and to identify the processors and products involved."
The source of the contamination is believed to be a licensed mill which manufactures animal feed.
The Irish minister for agriculture, Brendan Smith, said the problem was confined to 47 farms.
He said: "This includes 38 beef farms. This is the total number of farms identified as having received possible contaminated animal feed. There is only one feed supplier involved."
The FSAI's chief executive Alan Reilly said: "The levels in the feed were very high. The levels in the pork itself were in the region of about 80-200 times above the safe limits."
Labour Party spokesman on agriculture and food, Sean Sherlock, said the government's priority had to be consumers, but action had to be taken to "save the Christmas pork and ham market".
He said: "The announcement amounts to a threat to the overall viability of our food industry as great as, if not greater than, the outbreaks of BSE and of foot and mouth."
Padraig Walshe, president of the Irish Farmers' Association, described the recall as "an absolute disaster" for the pig farming sector, but said fewer than 10% of products on the market had been processed since 1 September.
"It will be possible to have fresh product - and totally safe product - on the shelves within a couple of days," he said.
Mr Walshe said up to 70% of Irish pork was consumed within the country itself - "a larger proportion" of the rest goes to the UK.
About 7,000 people are employed in the Republic of Ireland's pig industry, which is worth more than 250m euros (£216m) a year.
The British Pig Executive said that between April-July this year, the UK imported 230,000 tonnes of pork and bacon, with up to 15,000 of those from the Republic of Ireland.
A spokeswoman for Defra said it was "keeping in close contact with the FSA as they evaluate any potential implications for Britain".