A leading councillor has asked to see the evidence to a forecast that a massive wind farm project would create fewer jobs than previously predicted.
Barvas Moor is the proposed site for the LWP scheme
The Royal Society for the Protection of Birds (RSPB) commissioned a study that claimed the Lewis Wind Power (LWP) site would generate just 73 jobs if built.
Angus Campbell, of Comhairle nan Eilean Siar (Western Isles Council), has invited the RSPB to explain its study.
The RSPB said the Comhairle already had the detail backing its findings.
However, a spokesman said the charity would be willing to discuss the research with Mr Campbell in person.
The local authority backed the scheme despite receiving more than 4,000 objections.
Mr Campbell, the Comhairle's vice-convener, said there was "little evidence" in a press release issued by the bird conservation charity announcing the results of its research.
He also accused RSPB Scotland of making assumptions on the effect the project would have on tourism.
Mr Campbell said: "Obviously we will look at this study in detail but it does seem odd that their findings are so at variance with others."
He added: "Where is the evidence? I would also ask the RSPB why they are now concentrating on socio-economic factors when they have always argued that their remit is purely concerned with birds, not people.
"Perhaps the RSPB know their arguments on birds versus wind farms do not stack up, given that climate change is the biggest threat facing bird species."
The vice-convener said he would be writing to the organisation about its stance on a proposed wind farm development on Shetland.
Scottish and Southern Energy (SSE) have signed a partnership agreement with Shetland Islands Council.
The project, which depends on planning permission and a seabed cable, would see the building of a 200-turbine farm.
Mr Campbell said: "I am also writing to the RSPB to ask about their involvement with Scottish and Southern, the Shetland wind farm and their silence on the threat to birds from that scheme in which they have a direct financial interest."
RSPB Scotland commissioned global real estate adviser DTZ Consulting to carry out an economic assessment of the plan for Barvas Moor.
The charity has previously opposed the development because of its fears about birds flying into the turbines.
The RSPB said there were "crucial differences" with Shetland and LWP
Responding to Mr Campbell's comments, the spokesman for RSPB Scotland said the Comhairle should already have information backing its findings.
He said the RSPB's relationship with SSE regards the Shetland project stemmed from its praise for being "one of the greenest schemes on the market".
However, he said: "We do not benefit from new wind farm developments, as suggested.
"This arrangement does not in any way prevent us from raising concerns about SSE developments where they pose significant threats to birds."
The spokesman added: "The crucial differences between the Shetland scheme and the LWP proposal is that it is not located in an area protected by European law for bird life."
LWP - a 50/50 joint venture by engineering group Amec and British Energy Renewables - has defended its consultant's findings which claimed 233 jobs will be created once the scheme is operational.
Neil Evans, director of Regeneris Consulting which did the study for LWP, said its initial review of DTZ's research for the RSPB raised various concerns - but two in particular.
He said: "The first suggests that they didn't take the time to interview any of the economic development organisations in the Western Isles and therefore did not realise that the annual payments would be part of an investment programme creating jobs throughout the life of the wind farm.
"And the second is that they have chosen to predict a negative impact on tourism which is pure conjecture."