The Evening Press exclusively revealed on Tuesday how Scarborough, Whitby and Ryedale Primary Care Trust had launched an epidemiological study, comparing deaths by cancer in the area near the early warning station during the 1990s with average figures for the whole country.

The Trust reiterated today that no concerns had been expressed about cancer rates by local doctors or consultants; clinicians had not observed any changes in the frequency of diagnosis of various cancers.

It said the study had instead been launched in response to requests from the RAF base, local authorities and MPs, who had said it would allay public concerns.

CND, which has a long-running campaign against the base and its role in America's Son of Star Wars missile defence plans, and is planning to visit the inside of the base tonight, says it has raised serious concerns about both the levels of radiation and the limits set by the government.

Spokesman Neil Kingsnorth said: "This investigation is excellent news and we're glad that the Care Trust has put the interests of local people first.

"We would like to see a full investigation in to radiation levels at present, levels as they will be when the base takes part in missile defence procedures and an independent test of the National Radiological Protection Board's limits.

"We would also like to see a full probe into the health effects of this radiation - not just cancer rates, but all potential risks.

"This cancer probe is very welcome and we hope it is start of a wider investigation."

The epidemiological study will compare deaths by cancer in the area during the 1990s with average figures for the whole of North Yorkshire and England and Wales.

The investigation has been ordered by the Scarborough, Whitby and Ryedale Primary Care Trust in the wake of residents' concerns that radar emissions from the early warning station might cause cancer clusters in the vicinity.

Tim Lawn, a North York Moors National Park Authority member, suggested yesterday that there had been several unusual cancer cases, especially in the Goathland area.

"Health is the major issue locally," he said.

News that the Trust had already begun an investigation came as the authority agreed to press the Government to fund a long-term epidemiological study of the area, to establish if there were any disease clusters which might be attributable to the radars.

Authority members also agreed to push for the monitoring of radio frequencies in the area by independent consultants, following the base's upgrade as part of the USA's Son Of Star Wars missile defence project.

However, members doubted that the Ministry of Defence (MoD) would do as they were asking. "I am sceptical because I don't trust what this Government will do," said John Fletcher.

The Scarborough health trust's director of public health, Dr Jeffrie Strang, said residents' worries had been raised after a BBC documentary earlier this year had reported possible cancer clusters near a similar early warning station at Cape Cod in America.

Under the study, data held on the regional cancer registry would be used to compare the area around Fylingdales, and the whole of the PCT area, with the rest of the country, in an attempt to establish whether rates were higher, lower or similar to the national and regional average.

He believed the study, which would not include base employees, might take two or three months to complete. He pledged that the results would be made public.

Keith Mollison, a member of Fylingdales Action network, said news of the study was a "positive first step", but he felt the MoD should still fund a long-term study, as requested by the park authority.

Meanwhile, the authority has been told that the MoD wants to build an 800-square metre new police station at Fylingdales as part of a security upgrade at the base. The proposal will come back for discussion at a future authority meeting.