BT and Scottish & Southern Energy (SSE) have signed a new deal which will enable the utility supplier to provide voice and broadband services.
It is expected that the contract will allow SSE to provide service to around 8.5 million customers throughout the UK using BT's Wholesale service.
The three-year deal will support SSE's aim of becoming a "high-quality, national provider of integrated communications", BT states.
Using BT's existing network is expected to allow SSE to bring voice and broadband services to its customers quickly and with a minimum of financial risk.
Itret Latif, telecoms business manager at SSE, said: "[SSE] wanted a partner that could support us with the best suite of integrated communications services quickly, nationally and with minimal capital and operational risk."
SSE is looking to expand after its utility services attracted over 650,000 customers in the nine months to December 2007, establishing it as the UK's second largest provider.
It also reported a 22 per cent fall in customer complaints.