TELECOMS watchdog Ofcom is curbing prices on one of Openreach’s most popular broadband lines to encourage investment in superfast broadband.

It is cutting the whole price that BT’s infrastructure arms can charge rivals such as Sky and Talk Talk for lines with a download speed of 40 megabytes per second (Mbps) and an upload speed of 10Mbps. Prices will fall from the current £88.80 per year to £52.77 per year by 2020/21.

Ofcom said it expected companies to pass the costs savings on to customers through lower bills.

Jonathan Oxley, its competition group director, said: “Our plans are designed to encourage long-term investment in future ultrafast, full-fibre networks, while promoting competition and protecting consumers from high prices. People need reliable phone and broadband services more than ever. We’re making sure the market is delivering the best possible services for homes and business across the UK.”

Openreach will maintain full control over the prices for lines with an even faster speed in the hope it will spur telecoms firms towards installing their own superfast lines to rival BT.

The price controls come as part of a package of new rules demanding Openreach fixes faults and rolls out broadband lines at a quicker pace. As part of the measures, it will be expected to improve the level of fault repairs completed within one to two working days from 80 per cent to 93 per cent. Ofcom also wants 97 per cent of repairs to be completed within six to seven working days.

BT was hit with a record £42 million fine by Ofcom on Monday and is facing compensation costs to rivals of £300m over delayed high-speed cable installations.

However, Openreach questioned whether the price controls would lead to fresh investment in superfast broadband.

“The UK needs a regulatory framework that encourages investment and rewards risk,” said a spokesman. “Building digital infrastructure is very expensive with long payback periods and we won’t recover our more than £3bn investment in fibre until after this charge control period.

“We want to invest in more ‘full fibre’ infrastructure, and we’ll be consulting with our CP customers to develop new business models and support to achieve that.

“We support the ambition of higher service targets and we want to work closely with the rest of the industry to make sure these are the right measures and that they’re achievable.”

Talk Talk chief executive Dido Harding said the price cuts were welcome, but consumers will be left frustrated that they have to wait a year before they can benefit from lower bills.

She said: “Ofcom’s decision to only regulate some products also risks entrenching a speed divide, with customers having to make a false choice between fair prices or higher speeds.

“Ensuring consumers enjoy low prices on all superfast products is the best way to maximise take-up and encourage investment in the pure fibre infrastructure of the future.”

Dan Howdle, an analyst at broadband advice site Cable.co.uk, added: “By placing no such cap on prices charged for ultrafast (variously defined as speeds exceeding 100, 300 or 1000 megabits per second, depending on who you ask), investment in these faster technologies will be positively encouraged.”