FARMERS' leaders will this morning intensify their battle with National Grid by revealing new evidence linking overhead power lines with cancer.

The National Farmers' Union (NFU) will use today's high-profile North Yorkshire County Show to highlight fears over the possible health risks connected with a controversial pylon line to be created through the region.

Union chiefs will point to a new report from scientists at Bristol University, which claims to have uncovered another cluster of cancer cases among families living and working near overhead cables in the Cornwall area.

The study comes just over a month after NFU Northallerton branch secretary Peter Edmonds revealed that his own research had found a similar cluster of cases among farming families close to North Yorkshire's existing high voltage lines.

National Grid insists that 20 years of research has built up a wealth of evidence to show that overhead lines are not a health risk.

But last night, Mr Edmonds described the latest findings as "a bombshell" which would add further weight to the arguments of protestors fighting the creation of a 50-mile line of pylons from Teesside to Shipton, near York.

"The debate is heating up because we have the sword of Damocles hanging over our heads here," said Mr Edmonds.

He added that the NFU would do everything it could to maintain the pressure and keep the issue in the public eye.

Mr Edmonds also renewed his call for an urgent study into the possible health effects.

"I suppose it is up to the powers that be in National Grid, but with this report we have something new, hitherto unexplained, undiscovered, unreported and unknown about power lines.

"It is a big question mark hanging over them, but if they want to go ahead and build them, that's up to them."

Peter Johnson, of pressure group Revolt (Rural England Versus Overhead Line Transmission), said the new report was further proof that the line should not go ahead.

"It should be assumed that there is a potential danger and things that don't have to be done shouldn't be done, namely the North Yorkshire line."