The Ministry of Defence is fighting plans for two giant wind turbines over fears the towers could mark enemy jets entering British airspace.
Officials at the Ministry of Defence say the 115ft towers are so big they could look like planes on monitoring equipment.
The MOD say radar could classify the turbines as a threat – automatically sending in fighter jets to investigate and allowing real enemies to sneak in.
They say the green energy devices would confuse computer systems designed to protect the UK – and don’t want them put up.
Plans for the turbines have been submitted by Richard and Ian Lobb, who want to install the 50kW towers on their neighbouring farms in St Ewe, Cornwall.
But their application prompted a written objection from the MoD which warned the installation would cause “unacceptable interference” to an air traffic control (ATC) radar 30 miles away in Wembury, Devon.
Radar operators have to treat any unidentified object as a genuine threat – and could even have to scramble fighter jets to investigate.
Their objection said: “Wind turbines have been shown to have detrimental effects on the performance of MoD ATC radars.
“These effects include the desensitisation of radar in the vicinity of the turbines, and the creation of ‘false’ aircraft returns which air traffic controllers must treat as real.
“The desensitisation of radar could result in aircraft not being detected by the radar and therefore not presented to air traffic controllers.”
MoD chiefs said controllers relied upon accurate radar readings to distinguish between military and civilian aircraft.
Their letter added: “The creation of ‘false’ aircraft display on the radar leads to increased workload for both controllers and aircrews and may have a significant operational impact.
“Furthermore, real aircraft returns can be obscured by the turbine’s radar returns, making the tracking of conflicting, unknown aircraft much more difficult.”
The wind farm proposal has also provoked opposition from locals who say the towers will be a blot on the picturesque Cornish landscape.
Graham Chaplin, who owns a smallholding near the proposed site, has collected signatures of 109 villagers calling on Cornwall Council to reject the plan.
He said: “The turbine will really be right on top of us. It’s so close that we are going to suffer from noise pollution. But what’s more worrying is that there is a public safety issue with these turbines.
“The MoD clearly says that operators cannot assume that it’s just the wind turbine. They have to deal with it as if it was a real problem.”
Cornwall Council is due to report back on the application by May 13.
A spokeswoman said the council does not comment on undecided applications.