Makers of the meat substitute Quorn face legal action in the US from a consumer advocacy group which is claiming that the food can cause allergic reactions.

Avery Goodman, a business lawyer, from Fort Collins, Colorado and the Centre for Science in the Public Interest, have filed a suit in what is intended to be a class action against the company and Whole Foods Market, an organic and natural foods chain.

The centre alleges that many who eat Quorn foods will develop "unsavoury gastrointestinal symptoms" or more serious reactions. It has been fighting a long battle against the brand, sold in Britain since 1986 and the US since 2002, and runs a website eliciting consumer complaints.

The law suit has been filed in Travis county district court, in Austin, Texas, where Whole Foods is based. Quorn Foods Inc, the US subsidiary of UK-based Marlow Foods, accused the centre of "ridiculous tactics" in trying "to create publicity to undermine the credibility of Quorn over here".

David Wilson, Quorn Foods' vice-president and general manager, said: "Business is doing incredibly well. We have five of the top seven items in the meat-free market here."

Quorn Foods had followed the labelling advice of the regulatory bodies in the UK and US, he said.

Mr Goodman, an attorney in Fort Collins who handles securities fraud cases, alleges he experienced a five-hour bout of cramps, nausea, vomiting and diarrhoea, after buying a Quorn product at a local Whole Foods store.

"I had the impression it was a product derived from mushrooms, as this is the impression left by a light reading of the package. I am not allergic to mushrooms ... I am not allergic to anything in normal life, except, perhaps Quorn," he said.

He said he wanted warnings put on products. Two years ago, after complaints to the Advertising Standards Authority from the CPSI centre and the mushroom industry to the Advertising Standards Authority, Marlow Foods had to alter its labels which suggested the key ingredient of the food was mycoprotein, a mushroom protein. It is now described as "a nutritious member of the fungi family".

The Food Standards Agency says on its website: "Some people have reported allergic reactions to mycoprotein, but this is rare - research suggests that about one in 100,000 to 200,000 people will react to it.

"Because it is made from a fungus, it's possible that some people who react to other fungi or moulds (including when they breathe them in) may also react to mycoprotein."

Whole Foods Market said they would defend their company.