Pipex has sold its broadband and phone division to Tiscali for £210m.
The businesses being sold to Tiscali include Pipex Homecall, Pipex Internet, Switch Telecoms and Toucan Residential.
Peter Dubens, executive chairman of Pipex, said Pipex is continuing a strategic review of the company's other business divisions and reviewing its options for the distribution of the proceeds from the broadband and voice division to its shareholders.
He said that "in the consolidating UK market" the deal "crystallises value for shareholders" and ensures Pipex's customers will continue to receive a wide range of high-quality communications and internet services. The deal is conditional on shareholder approval and competition clearance being received.
Pipex is holding on to three divisions following the acquisition, namely its business services, web hosting and Pipex Wireless.
Pipex Wireless, a joint venture between Intel and the ISP, rolled out WiMax in Milton Keynes last year with a Warwick rollout on the cards for this year.
Pipex has expanded through a number of acquisitions in the last few years, including buying Bulldog Broadband and Toucan last year for £36m.