The company says the plan will also make the network able to handle 300 times its current capacity.
The changes are part of an already announced £5bn ($8bn) five-year investment plan.
BT is beefing up its Internet Protocol (IP) backbone: the telecoms equivalent of motorways along which data can travel at high speed before rejoining the normal telephone network for the last leg to an office, home or mobile phone.
Connection by most web users in the UK to their internet service provider (ISP) is currently made via a local call through BT, which controls the local networks.
Costly calls
The access is charged at the same rate per minute as telephone calls, and there have been complaints that internet growth in Britain has been restricted by the cost of connection.
In the US, low-cost one-off connection charges have helped boost the development of the internet.
On Tuesday, the UK telecoms regulator, Oftel, launched a campaign for lower net connection charges, saying they should better reflect actual costs to the provider and also offer greater flexibility.
The proposals come hard on the heels of BT's own internet call charging initiative, announced earlier this month, in which it opened up the prospect of offering flat-rate rather than metered pricing.
Huge growth
BT's mainly optical-fibre IP network is Britain's biggest, and the company says its growing use should lead to calls becoming cheaper.
Forecasts have said traffic generated from internet, e-commerce and multimedia services will rise by 400% a year.
BT says however fast net use grows, it will have the capacity to meet demand.
It says one in every four calls made across its networks is currently for internet access.
The IP dial-access market is forecast to grow to 30 billion call minutes by March next year, and to 140 billion by March 2004.
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