RSPB Scotland has lodged a formal objection to the Viking wind farm proposal on Shetland.
After scrutinising in detail the developer's application, assessments have revealed that there would be significant and unacceptable adverse impacts on many bird species should the development proceed as currently proposed.
The proposed Viking wind farm on Shetland is a partnership project between Scottish & Southern Electricity (SSE) and Shetland Islands Council.
It consists of 150 3.6MW turbines and 73 miles (117km) of tracks and would have an installed capacity of 540MW.
The RSPB said in a statement that significant numbers of nationally important populations of whimbrels, red-throated divers, golden plovers and merlins are likely to be displaced or killed by some of the turbines. Several of these species are given EU-protected status.
The environmental statement submitted by the developers also suggests that the effects on peatland habitats would be very damaging. It indicates that the predicted payback period for CO2 emissions is uncertain and RSPB Scotland finds the potential worst-case scenario of up to 48.5 years entirely unacceptable.
Lloyd Austin, RSPB Scotland's head of conservation policy, said: 'We very much appreciate the consultation that the developers sought with us at the early stages of the design and the effort they have taken to avoid SSSIs and other protected areas.
'However, now that we have analysed the full detail of the application, it is clear that a wide range of bird species will be affected. Furthermore, the lack of certainty that there would be any significant net CO2 benefits undermines the case for development; there is no point in building renewables that potentially emit more carbon due to peatland impacts than they save,' he added.
Austin continued: 'However, we would be prepared to review our position if these issues could be satisfactorily resolved. This is likely to require not only removal or relocation of turbines, but also a substantial increase in enhancement measures for biodiversity. Our formal response will have more detail on these matters.'