The UK Ministry of Defence (MoD) has objected to four proposed wind turbine sites due to interference with military radar.
The UK Government intends to build 7,000 wind turbines around the UK by 2020, providing 33GW of power.
The Department for Business, Enterprise and Regulatory Reform (BERR), responsible for UK energy policy, says there are "issues" over military radar and turbine sites, The Times newspaper reports.
An MoD spokesman says the military does not object to every proposal, but looks at each site on an individual basis.
"The MoD is committed to government targets for renewable energy and whenever possible we seek to work with wind farm developers to find a mutually acceptable solution," he says.
In 2004 and 2005, trials showed wind turbines create a 'hole' in radar coverage, making aircraft undetectable.
The height of the turbine, aircraft or radar station made no difference to coverage.
The BERR says it is working with the MoD to explore technical solutions to the problem.
By Elizabeth Clifford-Marsh