It's being described as the most important consumer rights case in history and could see thousands of products removed from sale, as well as billions paid out in compensation.
Papers lodged with the High Court in London, claim millions of people have been conned out of their money by some of the UK's biggest high street names over the last 50 years, because of fraudulent claims made by the products they bought.
"It sounds complicated, but essentially it comes down to this." Sylvia McGrouther, the solicitor handling the test case group action told reporters. "If you bought something that was hailed at the time as the best ever and were satisfied with it, only for that product to then be 'improved' upon and re-sold as the 'Best Ever', then I believe you've been the victim of a massive fraud."
"My clients say that if the firms behind selling something as a the best ever were serious, they would have waited until they'd got their formulation or recipe to it's zenith, before releasing it to the public. Otherwise, we claim, the firm is not only guilty of fraud, but also illegal experimentation on human beings, specifically outlawed by the United Nations."
Mrs McGrouther has some of the high street's biggest brands and firms in her sights, including Procter & Gamble, SC Johnson, Coca-Cola, Sony and Gillete.
"It's the razors that are perhaps the most galling. They claim to constantly be improving, so why have they consistently called each new product their best ever. It just highlights the fact they they've essentially released products before they've reached the final and therefore ultimate version."
The case is due to be hear later this year. None of the companies listed were available to comment.