COUNCIL leaders in North Somerset are to join forces with other authorities along the route of a proposed new power line to continue to campaign for the cables to go underground.

North Somerset Council is poised to sign a planning performance agreement (PPA) with energy giant National Grid to ensure the authority is fully involved with every step of the power line plans.

Other councils along the route – including Sedgemoor, West Somerset, Somerset and South Gloucestershire – have already signed the agreement.

National Grid wants to create a new 400,000-volt power line from Avonmouth to Hinkley Point to bring electricity onto its transmission network as part of the Hinkley C Connection Project.

The preferred route for the new line – which will mainly follow the route of the existing 132,000 volt overhead line on the western fringes of Nailsea and cut across swathes of the North Somerset and Somerset countryside – was announced by National Grid in September.

An independent report looked at the costs of the different options for the cables including overhead, underground and undersea insulated lines. The authors agreed with National Grid that the cheapest option for the new power line was overhead cables.

They put the costs of running the cables underground at between £10.2 million and £24.1 million a kilometre – a maximum of almost £39 million a mile.

North Somerset Council executive member for strategic planning, Councillor Elfan Ap Rees, said: "While we are disappointed that the subsea route appears not to be viable our challenge now is to minimise the environmental impact on residents and businesses.

"So it is vital that we now work with National Grid, local communities and other affected local authorities to secure the best outcome, in particular as much undergrounding as practical around Nailsea, Yatton and the Loxton gap."

National Grid has until 2013 to submit its proposals to the Government and a final decision will be made by the Infrastructure Planning Commission, the independent body which handles applications for "nationally significant" infrastructure projects such as power stations and airports.

Mr Ap Rees said: "We can still disagree and object to what is being proposed – this PPA does not mean that our ability to robustly challenge what National Grid is putting forward is curtailed, far from it.

"But what we need to do is be at the centre of things, influencing and cajoling, not shouting from the sidelines.

"Doing this gives us the best chance to work with interest groups, other councils, who no doubt will be facing the same issues as we will be, and with National Grid themselves."