The bakery company – Speciality Flatbread Ltd – ceased trading and went into administration in 2022.
None of the supermarkets detected the slavery while victims worked at the factory between 2012 and 2019.
Dame Sara said she would have expected the retailers to be doing “pretty thorough due diligence”, adding that they normally “take much greater care about their own brand products because that’s their reputation that’s on the line”.
Sainsbury’s said it stopped using the company as an own-brand supplier in 2016.
The others only stopped sometime after police rescued the victims in 2019.
Asda told the BBC it was “disappointed that a historic case has been found in our supply chain”, adding that it would “review every case identified and act upon the learnings”.
It said it had made three site visits, but focused solely on food safety, and had stopped using the factory in 2020.
Tesco said inspections – supported by information from anti-slavery charity Unseen – “revealed concerning working practices” and the company “ceased all orders from the supplier” in 2020.
Waitrose said it pulled out in 2021 after its audits led to “concerns about factory standards and working conditions”.
The Co-op said it made “a number” of unannounced inspections, including worker interviews, but found no signs of modern slavery, adding that the company “actively work to tackle the shocking issue… both in the UK and abroad”.
M&S said it suspended and delisted the company in 2020 after it “became aware of potential breaches of ethical labour standards via the modern slavery helpline”.
The British Retail Consortium said workers’ welfare was “fundamental” to retailers, who it said acted quickly when concerns are raised.
“Nonetheless, it is important that the retail industry learns from cases like this to continually strengthen due diligence,” it said.
