Telecoms giant BT signalled yesterday that it will fight proposals from regulator Ofcom to open up its high-speed network to direct “dark fibre” access by its rivals.

BT is already obliged to sell wholesale leased line products using its fibre-optic cables and network equipment to other operators.

But, in a move aimed at promoting competition in the £2billion leased line data market, Ofcom plans to allow other companies to access the cables directly.

This is referred to as “dark fibre” because the fibre-optic cables would not be “lit” by BT’s equipment but by a rival operator installing its own.

BT has faced criticism from competitors over the way it controls much of the UK’s telecoms network through its Openreach division, which some argue ought to be split off from the group.

Ofcom’s plans would require BT to make “dark fibre” available throughout the UK except in central London, where there is already deemed to be enough competition, and Hull, where most lines are provided by Kcom rather than BT.

The regulator said: “This should increase the opportunity for competitors to create tailored, high-capacity data links at cost-effective prices for their customers.”

Ofcom also proposes new quality-of-service requirements on Openreach, saying the wholesale provider often takes too long to install leased lines and too often changes the date on which it promises to deliver services.

However, BT insited that the market already allowed for fair competition, and warned that Ofcom’s proposals could have the opposite effect on competition from that intended.

“Openreach’s current offer creates a level playing field and a vibrant, competitive market with hundreds of competing companies, large and small,” said BT.

“Mandating dark fibre risks favouring a few companies that have the greatest capability to deploy it, to the disadvantage of all other firms.”

In contrast, rival TalkTalk welcomed the announcement, saying: “For too long BT has been able to get away with delivering poor service to Britain’s businesses at inflated prices and these recommendations will help drive competition.”

Ofcom’s proposals are subject to consultation until July 31, with final decisions due early in 2016 and taking effect in April next year.