Nisa is to join Co-operatives UK, the trade association for co-operatives and mutuals.
Nisa said it provides its small business members with buying power and a store support package including distribution services through its partnership with supply chain DHL. Nisa has a turnover of more than £1.5bn.
Neil Turton, Nisa chief executive officer, said: “As a member owned organisation, Nisa works for its members, providing them with significant benefits to help them develop their businesses.
"We are pleased to have become a member of Co-operatives UK and look forward to working with them to promote and develop co-operative enterprises.”