Incumbent fixed line carrier BT said Thursday it is halfway towards its goal of building a million strong wifi hotspot network in the UK.

The company said that public wifi is now available at 500,000 homes, businesses and city centres in the UK and Ireland.

The sites include hotspots provided by the BT FON community, set up by Spanish open wifi maverick Fon, in which BT is an investor; BT Openzone; and Openzone hotspots via the BT Business Hub, offered by brands such as the Hilton, Thistle and Ramada Jarvis hotels, Cafe Nero and Starbucks.

BT said that 4.8 million customers have inclusive network minutes in their contracts allowing to surf the net, work or make VoIP calls over wifi.

A further 50,000 hotspots are available in the UK and overseas through international roaming partners, BT said.

Fon launched at the end of 2005 and has managed to land funding from Google, Skype and top venture capitalists, Index Ventures and Sequoia Capital as well as BT.

Its users are divided into three and are known as either ‘Bill’ after Bill Gates, ‘Linus’ after Linux creator, Linus Torvalds, or ‘Alien’.

Bill members download software from Fon that turns their home wi-fi network into a hotspot offering anyone within its range, access to the internet for a fee.

Linus members allow their hotspots and bandwidth to be shared for free and can use any other members’ free of charge.

Aliens pay to connect to the Fon network and do not share their own networks. Fon and Bills will share the revenues earned from Aliens and other Bills.

The system has caused some disruption in the industry as a partly grass-roots social movement that encourages users to share internet access with their neighbours.