Greenwich council has signed a seven-year £6m network services deal with Logicalis.
The deal includes the upgrade and implementation of a local area network (Lan) and wide area network (Wan), and forms part of a borough-wide modernisation programme to improve internal operational efficiencies.
The IT network will also support new e-services for use by citizens and visitors to the London 2012 Olympics.
Councillor Peter Brooks, deputy leader of Greenwich council, said, "The decision to outsource the day-to-day operational maintenance of the network will enable us to focus on delivering applications and services that streamline existing processes. It makes absolute commercial sense for us to outsource operational and commoditised tasks to a trusted IT partner."
10,000 council employees will be migrated over to the new converged voice and data network over the next 12-18 months.