The company's IT director, Gordon Scholes, said outsourcing had allowed management to focus on the core business and removed the need to invest in the recruitment, retention and training of IT staff.
"The simplification and rationalisation of our communications infrastructure is playing a crucial part in our five-year strategic plan and we can rely on BT to deliver first-class services as well as cost savings for our business."
Under the deal, BT is responsible for Somerfield's communications services, some internal support capability and the network connecting 1,330 stores and 23 depots. It has also developed a billing service which provides a single bill and report covering all Somerfield's networks and 15 service and equipment suppliers.
The next project is developing new hi-tech mobile technology.