BT has said that a proposed 50p per month levy on phone landlines will not provide enough funds to cover the entire UK with fibre-optic broadband. However, the company is prepared to guarantee a 15Mbit/s service where fibre-optic is available.

At a briefing to discuss the next phase of BT's fibre-optic rollout today, BT strategy and portfolio group director Liv Garfield said that the levy, proposed in Lord Carter's Digital Britain report last month, would probably not provide enough funds to deliver fibre-optic broadband to the entire country.

"There's £1bn on offer here, but the devil's in the detail about which areas will get funded," she explained.

"If you're going from 55 to 85 per cent, then I can see that that could be delivered. I can see a way to get to 80 to 85 per cent with that kind of money, but we will struggle to get to 100 per cent – in fact it would be impossible to get to 100 per cent."

However, in answer to a query regarding service level agreements (SLAs), Openreach managing director for next-generation access David Campbell said the company will guarantee 15Mbit/s, and take steps to remedy the situation if the service delivered falls below this.

Traditionally, carriers have declined to offer SLAs on broadband connections, leaving smaller companies to choose consumer-grade broadband offerings or opt for more costly services backed by an SLA.