Scottish Natural Heritage (SNH) has warned that the huge Ardchonnel wind farm in Argyll would have "significant adverse impacts" on local villages and the skyline, spoiling the countryside "for residents and visitors alike". It also says the development is "out of scale" with the surrounding landscape.
The Ardchonnel scheme, which is being developed by German energy firm RWE Innogy, is on a 3500-acre estate owned by Tory MSP Sir Jamie McGrigor, who stands to earn more than £300,000 a year in rent for 25 years if the project goes ahead.
The scheme would see 15 turbines 111m (364ft) tall erected above Loch Awe, generating up to 45 megawatts - enough to power 40% of the homes in the Argyll and Bute Council area.
It has been denounced by dozens of McGrigor's constituents, who fear it will be a noisy eyesore and kill the local tourist trade.
The nearby hamlet of Dalavich could become a "ghost village", residents have warned.
McGrigor, 64, an Old Etonian baronet who has been a Highlands and Islands list MSP since 1999, insists the project would help the local community and provide jobs.
"The proposed location is in an area which has been identified as suitable for a renewable development of this kind," he told the Sunday Herald earlier this month.
Although SNH has not formally objected to Ardchonnel, its official advice is scathing.
In a submission last week to Argyll and Bute Council, which is handling the planning application, SNH says the proposal "will have significant adverse visual impacts" when viewed from some villages and parts of the loch.
The proposal is "not in keeping" with local wind farm advice, "nor Scottish planning policy" it says.
If approved, the wind farm would become a "dominating feature in views from Dalavich and Inverinan from where it will be overwhelming both horizontally and vertically in the undulating skyline".
It goes on: "A wind farm development of this scale is likely to undermine the landscape experience of enjoying the countryside for residents and visitors alike.
"We advise that this proposal is out of scale with the receiving landscape and is likely to undermine the landscape character."
Viewed from the north and north-west, Ardchonnel would be seen alongside the smaller An Suidhe wind farm "creating a confusing image of differing turbine sizes and rotations".
Sited in an area used by six rare bird species - golden eagle, red throated diver, white-tailed eagle, osprey, merlin and peregrine falcon - the development would also "contribute to the degradation" of bird habitats in Argyll.
Even with mitigation, "we consider that the impacts of the wind farm, whilst reduced, will remain significant and adverse", SNH concludes.
Argyll and Bute Council is due to consider the application before the end of May.
In 2008, McGrigor signed a parliamentary motion demanding wind farms rules to end "speculative applications ... threatening scenic areas".
However, in 2011 he struck a deal to let RWE erect a wind farm on land used for sheep grazing. If the plan is approved, he would receive £7000 a year for each megawatt of installed capacity, or £315,000 a year for the 45MW proposed. Index-linked over the 25-year life of the turbines, that would make him more than £8m.
RWE Innogy said: "SNH as statutory consultees have reviewed the application and provided comments that we are now considering. However, SNH have not objected to the development."
McGrigor said: "While I understand that some object to this development, there are many others who are very supportive, including two community councils.
"It has the potential to be of substantial benefit to the community, providing an annual income that will make the area more sustainable, while providing valuable jobs.
"I'm reassured the appropriate environmental impact studies have been carried out."