By Martin Shankleman
BBC employment correspondent
Saphire Trading provided workers to Barfoots of Botley, a Tesco supplier.
A gangmaster who provided labour to food suppliers of Tesco has been stripped of his licence.
Jagjit Singh, who ran Saphire Trading in Southampton, is said to have created an "atmosphere of fear and intimidation in the workplace".
The Gangmasters Licensing Authority said workers were subjected to "systematic exploitation" which placed them at risk of injury or death.
Tesco said it had been "very concerned" about the instances raised by the GLA.
The GLA has revealed details of the recent hearing at which Mr Singh was stripped of his licence.
They concluded that he showed "a wholesale and blatant disregard of licensing standards".
The GLA says Saphire Trading:
• withheld pay
• made illegal deductions from wages
• paid below the minimum wage
• failed to grant sick pay
• housed workers in property which was a danger to residents, as they lacked gas safety certificates, fire exits or extinguishers
• had employees working excessive and illegal hours
• failed to provide proper pay slips
• failed to provide health and safety training
• made workers provide own protective clothing
• failed to keep proper personnel records including NI numbers and permits to show their entitlement to work in the UK.
The hearing was told that workers, from Poland, were afraid to give evidence to the inspector for fear of losing their jobs or accommodation.
The GLA uses a points system to calculate the extent of breaches in its licence.
A score of 30 counts as a fail, and Saphire Trading reached a total of 185 points.
The GLA chairman Paul Whitehouse praised the courage of employees who helped with the investigation.
"It is the bravery of the workers who suffered at the hands of Saphire Trading in coming forward and making statements to the GLA that helped us to get this result," he said.
Tesco said it had been "very concerned last year about the two instances raised by the GLA and played an active role with our suppliers in supporting the investigation."
The company said it was working with GLA to devise a new code of conduct which includes joint sites visits to help eliminate worker exploitation in the supply base.
Saphire Trading provided workers to Barfoots of Botley.
Barfoots, based in Bognor, said it had sacked Saphire as a labour supplier and taken "immediate action to ensure employment continuity for all staff concerned".