The benefits of BT's upgrade to its existing copper network could reach only 17.7 per cent of Britain, depending on the type of connections used, a review comissioned by Ofcom has revealed.

The review examined a range of technologies and approaches that could be deployed in the rollout. And it covered the benefits and drawbacks associated with each deployment scenario.

If modems were stored in exchanges, 17.7 per cent of households would receive speeds above 50Mbps, and only 6.1 per cent would receive speeds above 100Mbps.

But if modems were installed in street cabinets, 99.1 per cent of households would receive 50Mbps or more and 95.5 per cent would benefit from speeds above 100Mbps.

In its conslusion, the regulator stated: "At the time of writing, Ofcom is not aware of any practical implementations of the technology approaches implied in this report that would lead to substantial increases in speeds being achieved on BT's copper network."

"Neither is there any indication that the changes and standards implied in this study are being considered by the relevant bodies."