Supermarket chain Asda is considering whether to cut the salaries of its 7,000 employees in the southeast of England to bring them in line with its other stores.
Employees at 39 stores outside the M25 have been paid more for decades to make up for the higher cost of living near London.
A company spokesperson said that all Asda employees recently received a 10% pay increase to help with rising inflation.
The GMB union said Asda would fire workers who refused to agree to the new conditions.
The union said the workers were already underpaid, and planning to cut wages during the cost of living crisis was “unforgivable”.
GMB said workers receive a so-called “site supplement” of 60p an hour, which Asda may get rid of, and a night supplement it wants to reduce.
She added that those who do not agree to the wage reduction “could be dismissed if they refused to sign” the new contract.
Consultations are currently taking place, the federation said, and Asda plans to introduce the changes in November.
It accused the Issa brothers’ owners of Asda of paving the way for a “debt-ridden merger” between UK fuel stations Asda and EG Group – which the brothers also own.
“These slash-and-burn tactics, along with increases in food and fuel prices, will only increase if consolidation continues,” said Nadine Hutton, GMB organizer.
However, an Asda spokesperson said group counseling was “in a small number of shops” with workers being paid 60p an hour on top of the national £11.00 an hour.
“This accessory is out of line with the broader retail market and has created an anomaly where some Asda colleagues in stores close to each other receive different rates,” said the spokesperson.
Asda is discussing a “compensatory payment” for removing the appendix.
The spokesman added: “These discussions are ongoing and no final decision has been taken.”
Asda has about 140,000 employees in total.