- Video report by ITV News Consumer Editor Chris Choi
Tesco is reportedly facing a bill of up £4 billion after lawyers launched legal action over equal pay.
The suit against the supermarket giant is on behalf of female shop assistants who claim they are paid less than male counterparts for work of equal value.
It is said that male warehouse workers are paid in excess of £11 an hour compared to £8 for females who work on shop floors - a difference of £3 an hour.
Over the course of a year male distribution centre workers take away £5,000 more than females doing the same hours, Leigh Day claims.
Tesco said they work hard to ensure all staff are paid "fairly and equally".
Paula Lee, from Leigh Day, representing the Tesco women, said: "We believe an inherent bias has allowed store workers to be underpaid for many years.
"In terms of equal worth to the company there really should be no argument that workers in stores, compared to those working in distribution centres, contribute at least equal value to the vast profits made by Tesco, which last year had group sales of £49.9bn."
Conciliation body Acas has been submitted the claims.
Similar suits are also taking place against supermarket rivals Asda and Sainsbury's.
A Tesco spokesperson said the company had not received the claim, but added: "Tesco has always been a place for people to get on in their career, regardless of their gender, background or education, and we work hard to make sure all our colleagues are paid fairly and equally for the jobs they do."