Major UK supermarkets including Tesco, Aldi, Asda and Lidl are being urged to stop using controversial “fake farm” branding on own-brand meat products, with a food charity claiming they are misleading shoppers.

The Feedback charity is backing the owner of a genuine farm called Woodside Farm – a name Tesco has also used on its value pork range since 2016 – and is threatening legal proceedings if the retail giant does not drop the name Woodside Farms.

Its “Total Bull” campaign says it believes shoppers are being misled with “disingenuous” branding that gives the impression it comes from real farms.

“Let’s be clear – supermarkets are selling meat under fake farm names, deliberately encouraging consumers to believe that the meat is sourced from small-scale producers,” said Feedback’s campaign director, Jessica Sinclair Taylor. “We believe this is peddling a load of bull.”

In March 2016 Tesco, the UK’s largest retailer, sparked controversy after launching a budget range of seven own-label “farm” brands – including Woodside Farms and Boswell Farms for fruit and veg as well as meat – based on British-sounding but fictitious names. Some foods were imported from overseas and given British names to make them sound local.

In April, Asda reignited the row by relaunching its value Smart Price food range as Farm Stores while German discounter Aldi replaced its Wood Farm brand with Nature’s Pick earlier this year and Lidl has a “Birchwood Farm” meat range. Marks & Spencer sells “Scottish Lochmuir” smoked salmon and “Oakham” chicken – neither are real farms.

Richard Baugh of Woodside Farm in Nottinghamshire, raises free-range pigs for his own pork products sold under his farm name through his farm shop and website. But since Tesco replaced its Tesco Value brand with “Woodside Farms”, he says he has faced confusion from customers.

“We’ve been raising pigs at Woodside Farm for 20 years – this is our livelihood,” Baugh said. “When it first came out customers were asking all the time whether we were supplying Tesco. We don’t, our pork is free-range and we think it’s higher welfare and quality than the pork they’re selling, and we’re proud of that.

Feedback wrote to Tesco on behalf of Baugh, complaining that its labelling risks confusion with his farm name and reputation, while misleading consumers about the origins of their meat.

The non-governmental organisation, which is seeking to reform Britain’s “broken” food system, has also awarded Tesco its “Total Bull” award for the number of fake farm labels it uses, and is urging shoppers to write to Tesco to shame it into dropping the branding.

Tesco said it was aware of the threat of legal action and declined to comment, but directed the Guardian to the publication of its interim results for 2017/18 when it said: “Our exclusive fresh food brands continue to be popular with customers – featuring in over 70% of baskets.”

The National Farmers’ Union (NFU) and the Soil Association have also condemned fake farm brands as misleading for consumers and insulting to farmers. Last July, the NFU filed an official complaint about Tesco’s brands with Trading Standards, but the non-existent farm staple remains on supermarket shelves.