Recently the Danish government ruled all turbines over 45metres needed a harness ascent aid for workers.
According to Danish wind power magazine Naturlig Energi, Vestas then sent out letters to domestic owners of its turbines promoting its own system.
However, the letters also went to owners of turbines under 45metres and added: "Vestas reserves the right to terminate the service agreement if the device is not fitted."
In response, one wind turbine owner said: "It's nice that Vestas want to improve the working conditions of their workers but maybe they should install the climbing aid themselves rather than use shotgun tactics."
After 14-days, Vestas sent another letter to owners who had not responded. It was only after complaints from owners of turbines under 45metres that Vestas sent a further letter retracting the threat and apologising for the earlier correspondence.
It stated: "[Vestas] very much regrets the wording of the said paragraph and the uncertainty this may have caused and looks forward to continued good co-operation."