Argos has dished out £1.5 million to staff they underpaid following a government investigation.
The firm failed to pay some 12,176 employees the National Minimum Wage or Living Wage.
Taking into account former workers too, staff found themselves £2.4 million out of a pocket.
Argos, bought by Sainsbury's last year, was the worst of 233 employers which did not pay staff the minimum wage, an investigation found.
More than 13,000 low-paid workers across the UK are now in line for back pay worth around £2 million.
Business minister Margot James said: "It is against the law to pay workers less than legal minimum wage rates, short-changing ordinary working people and undercutting honest employers.
"Today's naming round identifies a record £2 million of back pay for workers and sends the clear message to employers that the Government will come down hard on those who break the law.
"Common errors made by employers in this round included deducting money from pay packets to pay for uniforms, failure to account for overtime hours, and wrongly paying apprentice rates to workers."
Supermarket Sainsbury's flagged the error shortly after their takeover of the catalogue retailer.
The shortfall was linked to the timings of staff briefings before they had clocked on to their shifts, and security searches which could happen after workers had finished a shift.
All the staff have now received their back pay.
John Rogers, chief executive of Argos, said: "Shortly after we (Sainsbury's) acquired the Argos business last year it was brought to my attention that, as part of a routine visit, HMRC had uncovered an issue with some Argos store systems and processes, which meant that some colleagues had been paid below the national living wage.
"Sainsbury's prides itself on being a trusted brand where people love to work and I was, therefore, very disappointed to hear this and launched an immediate investigation."