BT and FON have promised to "transform the UK's market for wireless broadband" by launching BT FON, the world’s largest Wi-Fi community.
BT's three million consumer Total Broadband customers will be invited to join the global community of people sharing their broadband.
At launch, new members will be part of an existing community of 500,000 members and will have access to more than 190,000 FON hotspots worldwide.
Anyone joining in will be able to use those FON hotspots across the world and all the new BT FON hotspots free of charge.
BT says the revolutionary idea for a massive Wi-Fi community, built by individual people and not a large corporate enterprise, marks thier "boldest step yet" in building broadband coverage outside of the home or office.
Every person who agrees to share a small portion of their home broadband connection, by opening up a separate, secure channel on their wireless router, will be able to share the connection of any other member.
BT Total Broadband customers will also be able to use BT's premium existing hotspot network BT Openzone, including 12 Wireless Cities.
BT FON aims to build a huge community Wi-Fi network, covering hundreds of thousands of hotspots, in a short space of time, under the slogan "Wi-Fi for everyone, I’m in".
Gavin Patterson, BT Group managing director, Consumer, said: "This is the start of something very exciting for BT. Today we are launching a people’s network of Wi-Fi, which could one day cover every street in Britain".
"We are giving our millions of Total Broadband customers a choice and an opportunity. If they are prepared to securely share a little of their broadband, they can share the broadband at hundreds of thousands of FON and BT Openzone hotspots today, without paying a penny."
"We have built a public Wi-Fi network and 12 Wireless Cities already, but today we are saying to customers, let’s build a Wi-Fi community together, which covers everywhere and serves everyone."