The conservative American Energy Alliance (AEA) and National Center for Public Policy Research (NCPPR) jointly released a report on Thursday questioning the validity of a job study conducted for the American Wind Energy Association by Chicago-based Navigant Consulting.
The Navigant study, which found the US stood to lose 37,000 wind energy jobs in 2013 if the PTC was allowed to expire, was cited repeatedly during AWEA's push to keep the credit alive.
But the AEA accused the Navigant report of containing faulty modelling and biased wind capacity forecasts, which "vastly overstate" the potential job losses.
An AWEA spokesman said: "The PTC has clearly proven its effectiveness in driving dramatic growth in construction and manufacturing jobs.
"It is not surprising that these known opponents of clean energy challenge the numbers of a leading economic and energy consulting firm — they did the same thing with the Bureau of Labor Statistics estimates — and there are obvious and glaring flaws in their claims."