NATIONAL park chiefs are to take legal advice over the plan to upgrade Fylingdales early warning base for the US Son of Star Wars project.

In the wake of the Ministry of Defence's (MoD) agreement to the scheme, park bosses want to know more about the implications of its intensified use. They plan to seek advice from the Department for the Environment and Rural Affairs and the Countryside Agency regarding the MoD plan.

Members of the authority have expressed concerns over the possibility of extra radiation and the intimidation of walkers using the rights of way footpaths near the base.

Chairman Helen Schroeder, vice-chairman Herbert Tindall and other members have met Defence Secretary Geoff Hoon about the issue but are still waiting for a response.

Chief executive Andy Wilson told an authority meeting they should debate the issue on the lines of planning and the environment, and not other aspects of the upgrade which might concern other bodies.

"The MoD says it will not need planning permission as most of the changes are internal but we don't have any details as yet," he said. The authority has received a letter from the director general of International Security Policy, Nicholas Witney.

He said there would be no change to the primary function of the radar - surveying and tracking objects in the upper atmosphere and space - but the upgrade would give it additional capability, when required.