As well as cutting costs, the network, based on technology from BT, will provide greater bandwidth to Debenhams stores, meaning new initiatives and applications can be rolled out more quickly, the retailer said.
The implementation, delivered by BT Global Services, includes voice over IP, IP Clear and ADSL lines to stores and a Cisco wireless network in Debenhams' flagship store in the Bullring in Birmingham.
Martin Wyke, IS director at Debenhams, said, "The network gives us four times as much bandwidth as we had before, at a lower cost. It will allow us to centralise and standardise the management of services, driving down costs.
"We are putting voice on to the IP network in the first quarter of next year. Telephony will, in effect, be free because we are paying for the bandwidth, not the calls."
Debenhams has been rolling out technology to improve both its internal and external communications over the past year.
Earlier this year, the retailer embarked on an ambitious project to implement a private B2B portal for its suppliers to enable stores to react more quickly to changing demand.
The B2B portal, which is based on Microsoft .net, was initially aimed at Debenhams' international suppliers, but it is expected to include all the retailer's external partners in due course.
"The portal has been received well," Wyke said. "We are using it to work collaboratively on issues such as digital design, event tracking and purchasing."