The BBC has found signs that victims of modern slavery were being forced to work at a McDonald’s branch and a factory supplying bread products to major supermarkets.
The BBC says the situation was missed for years.
A gang forced 16 victims to work at either the fast-food restaurant or the factory – which supplied Asda, Co-op, M&S, Sainsbury’s, Tesco and Waitrose.
Well-established signs of slavery, including paying the wages of four men into one bank account, were missed while the victims from the Czech Republic were exploited over more than four years.
McDonald’s UK said it had improved systems for spotting potential risks, while the British Retail Consortium said its members would learn from the case.