The law firm is lodging complaints with the conciliation service Acas on behalf of almost 100 staff, paving the way for an employment tribunal process which has already led to similar, continuing claims against Asda and Sainsbury's, involving thousands of staff.
Leigh Day believes more workers will join the Tesco case as it progresses, given success to date in the action against Asda which the chain is due to appeal.
The law firm said the complaint against Tesco centres on allegations that store assistants have been paid £3 an hour, or £5,000 a year, less than their male warehouse counterparts, who are on around £11 an hour for essentially the same role.
Tesco shares were more than 1% down after the case came to light but later turned positive amid a wider market rally in the wake of the correction in stock values.
A spokesman responded: "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."
The law firm's Paula Lee, who is representing the Tesco workers, 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.
"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."