Supermarket giant Tesco could be forced to pay up to £4 billion over an equal pay row, a top law firm has claimed.

Lawyers from Leigh Day have launched legal action against the company on behalf of primarily female shop assistants who claim they are paid up to £3 less an hour than male workers in the company's warehouses.

The alleged disparity could see a full-time distribution working on the same hours earning more than £100 a week or £5,000 a year more than the mainly female store staff.

The law firm has announced the legal proceedings could be the largest ever equal pay challenge in UK history, which could cost the supermarket £4 billion in compensation.

Tesco could have to pay a fine of £4 billion

Lawyers from the firm have confirmed they have already been approached by more than 1,000 employees and ex-employees of Tesco.

It is not known if any of these worked at Tesco stores in Burton, Swadlincote, Ashby or Uttoxeter.

Paula Lee, from the law firm, told our sister paper, The Mirror: "We believe an inherent bias has allowed store workers to be underpaid for many years.

"In terms of equal worth to the company, there should be no argument that workers in stores, compared to those working in distribution centres, contribute to at least equal value to the vast profits made by Tesco, which last year had group sales of £49.9 billion.

"In the week where we have marked the 100-year anniversary since women began to get the vote, the time has come for companies and public organisations to have a long hard look at themselves, to see the inequality which is still deeply entrenched in their organisations."

Tesco said they work hard to ensure all staff are paid "fairly and equally."

A spokesman for Tesco said: "We are unable to comment on a claim that we have not received.

"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."