More than four years ago BT predicted it would only be serving five million broadband customers by the end of 2006.

More than 200 companies resell broadband from the telecom firm's wholesale and Openreach arms.

Companies such as Pipex, Virgin Retail and BT Retail are customers of the wholesale arm. Larger firms, such as BSkyB, effectively set up their own high-speed links from Openreach under a system known as Local Loop Unbundling.

This involves the link between telephone exchanges and customer's homes being handed over to BT's rivals instead of just being leased.

In November 2006 the number of local lines taken away from BT in this way topped one million.

BT Retail is thought to have about three million customers for its broadband service. This is roughly the same number of customers claimed by cable companies such as NTL/Telewest.

The continuing growth in UK broadband numbers is thought to be the result of several factors. Improvements in technology mean that people living in areas once thought to be beyond the reach of high-speed links can now use them.

Also stiff competition among UK broadband companies has pushed down prices and tempted many to sign up for what used to be a premium service.

Analysts Point Topic predict that broadband numbers will continue rising in 2007.

"Our latest survey shows there is still a big latent demand for broadband in the consumer market," said Tim Johnson, chief executive of Point Topic.

Mr Johnson said there could be as many as 2.5 million customers up for grabs in the first six months of 2007.