Broadband speeds differ widely across the UK
BT has launched a broadband service that offers speeds of up to 40 megabits per second (Mbps).
Based around fibre optic cables, BT said the Infinity service could change the way that people use broadband.
It will give some customers an upload speed of up to 10 Mbps. Trials have been held in London's Muswell Hill, Whitchurch and Glasgow.
BT said that four million homes and businesses would be able to get it by 2011.
The current highest speed service from BT available to homes is 20 megabits per second (Mbps), though not all homes can get this headline speed.
BT Retail said the basic 40Mbps service will be offered for £19.99 per month on an 18 month contract. It will also charge an installation fee of £50 for those on the lowest tariff.
Only those who opt for BT's most expensive tariff, £24.99 per month, will get the 10Mbps upload speed. With the basic package upload speed is up to 2Mbps.
BT said the higher speed would make it easier to share broadband among multiple computers and improve video streaming and net TV services.
As with lower speed services only those closest to the street cabinets that the fibre connects to are likely to get the full 40Mbps.
A spokesman for Virgin Media wondered why anyone would buy a service from BT that has yet to launch when it could get higher speeds via cable already.
He said Virgin was already trialling future technology that could see cable speeds reach 200Mbps.
The fibre service is being rolled out by BT's Openreach arm and will be offered to other ISPs to re-sell.
"Other providers may have differing prices," said Andrew Ferguson of Think Broadband. "Some higher if their fair use policy is more lenient, perhaps offers with lower prices if usage amounts are lower."
BT Retail said customers of the cheaper Infinity service would be limited to downloads of 20GB per month. Those paying more will get an unlimited service.
"The Openreach products that Infinity is based on, are available to the LLU providers, so we can expect to see products from TalkTalk and Sky in due course," he said. "As for when depends on whether they see customers moving."
Think Broadband is maintaining a list of exchanges that are fitted with the fibre technology so people can check if it has come to their area.
Mr Ferguson described the launch as a "step in the right direction".
"There is a chance for those in areas where these products and Virgin's 50meg is available to show that there is demand for products like this," he said. "That will encourage investors to put up more money so that the commercial led roll-outs can enlarge on their current plans."