Thus Plc, the UK-based telephone network operator, has put Demon, its internet service provider, up for sale. 

Demon, which was one of the first internet service providers in the UK, was acquired by Thus in 1998 for £66.6m. At the time, Demon had around 180,000 dial-up customers and was one of the UK's most popular ISPs.

Thus reportedly received an approach for Demon's domestic operations, which prompted it to issue an information memorandum to other potential buyers. 

Demon's small and medium-sized business operations will not be included in the sale, which analysts predict could fetch between £15m and £20m. 

Carphone Warehouse and BT have both been named as likely bidders.

Around 50,000 people in the UK currently subscribe to Demon's broadband package. The company has struggled to maintain profit levels of late, reporting a 15 per cent drop last year. This is partly due to customers upgrading from dial-up services to all-inclusive broadband tariffs.