Ofcom has begun an investigation into the cost of upgrading large parts of the UK to a high-speed fibre-cable network that will support next generation broadband.

Ofcom's consultation will look at how best to upgrade the current copper network as well as regulating the new networks, and will run until 25 June. The review comes alongside proposals to promote next generation broadband networks for new housing and office developments.

Ofcom's chief executive, Ed Richards, in a speech delivered to the Institution of Engineering and Technology, has suggested that one way to roll out fibre could come from running fibre in existing electricity or water pipes, or even the sewer network.

Using existing infrastructure means fibre can be rolled out at a fraction of the costs involved if roads had to be dug up. A number of companies in the UK are already using the sewers to roll out fibre. Geo already operates an 80km optical fiber network based in Thames Water's London sewer system.

"The large trunk sewer network in London's Victorian sewer system is ideal for the installation of high-speed optical fibre," said Chris Smedley, chief executive of Geo.

"There's plenty of headroom down there for installation and the cables can be pinned to the ceiling of the sewers out of harm's way, making it very secure."

He added that sewers offers a more secure network as they are built away from other optical fibre networks and would eliminate "the disruption and loss of service," which results when new street trenches are created.

This, he believes, makes a sewer-based fibre network an ideal solution for large businesses.

However, Smedley says it is unproven whether sewer-based networks will deliver these same advantages for residential areas. Geo points out that the sewer systems in outer London and other cities, not to mention suburban and rural locations, are a very different proposition as they're much smaller or, in some cases, nonexistent. He also warned that dealing with utilities such as Thames Water, requires significant planning before installation and a very high level of cooperation throughout the maintenance of the network.

"The sewer companies will not tolerate new network deployment if it impairs their own ability to provide services," he added.

Ofcom is facing increasing pressure not just from government ministers calling for investment in a high-speed next generation networks, but from ISPs concerned that the UK's copper-based network is creaking under the pressure from carrying bandwidth-hungry applications such as the BBC's iPlayer and websites such as Google's YouTube.

Indeed, the Government announced in late February an independent review headed up by the former boss of Cable & Wireless, Francesco Caio, to examine the issue of next-generation networks. Completion of this review is only expected in the autumn however.

BT said last year that it would consider rolling out fibre, but only if the economics were right. In reality, BT could not justify to its shareholders the estimated £7bn to £16bn costs needed to roll a next generation fibre network, without some form of incentive.