The supermarket chain Somerfield is cutting at least 500 jobs at its head office in Bristol.
The cuts follow the company's decision to sell off the loss-making Kwik Save brand together with 171 stores.
It is understood the redundancies could be at all levels, from managers to office staff.
A total of 1,800 staff are employed at the company's Whitchurch headquarters. A 90-day consultation with staff and employee representatives has begun.
The company plans to rebrand 102 Kwik Save stores and 140 Texaco forecourt stores as Somerfield.
The remainder were sold to Huddersfield-based BTTF, a new company specifically set up to operate Kwik Save.