The Co-op has confirmed it is shutting down Somerfield's head office in Bristol, putting 750 jobs at risk as it seals the billion-pound deal to purchase the chain.
The Co-op scooped up Somerfield last July for £1.57bn - and the deal should be completed in early March.
Somerfield will then be integrated into the Co-op business and the brand phased out over a two-year period.
The acquisition transforms the Co-op into the UK's fifth-biggest grocer, with 3,000 stores, and enables it to compete effectively with its bigger rivals.
The news came as the Co-op announced it had completed its acquisition of the chain, giving it an 8% share of the UK grocery market and sales of £7bn.
"This is great news for customers of both The Co-operative and Somerfield. It is a transformational deal, which cements our position as the UK's number one community retailer and returns us to the premiership of food retailers. It is no longer the Big Four, it's the Big Five," said Peter Marks, chief executive of the Co-operative Group.
"Our first priority now is to start integrating the two businesses - something that will bring real scale benefits, enabling us to provide better value to our customers. There is a strong strategic fit between these businesses and we are looking forward to creating a single business combining the inherent strengths of both Somerfield and the Co-operative Group.
"Somerfield has some great people and we are delighted to welcome them to the Co-operative family."
The enlarged food business will be headed by the group's managing director for food, Tim Hurrell.
Somerfield's Bristol headquarters will be retained for about 18 months, while all head office functions are moved to Manchester on a phased basis. Relocation opportunities will be offered to as many staff as possible, the Co-op said.
Commenting on the The Co-operative Group's acquisition, Paul Mason, chief executive of Somerfield, said: "The Co-operative Group is buying a business that is in rude health, with strong, positive like-for-like sales, and a profit margin that has doubled since the business was taken private in 2005."