The UK now has six million unbundled lines offered by 30 different providers, according to new figures.
Research conducted by Ofcom revealed that the UK's broadband market has "reached a significant milestone" and that competition is increasing.
In 2005 there were just 123,000 unbundled lines in the UK, before BT Group set up its Openreach division that allowed rival firms to offer services over its copper telephone network.
According to Ofcom, the rise in the number of unbundled lines has helped to reduce the cost of fixed-lines and increase the popularity of broadband.
The communications watchdog revealed that 67 per cent of homes now have a high-speed internet connection.
Ofcom Chief Executive Ed Richards said: "In just four years unbundling has gone from a flicker on the dial to a major competitive force in telecoms.
"This has delivered the dual benefits of driving up broadband take-up and driving down prices."