The 91-page State Government Planning Assessment Commission report that found against Bickham listed nine problems with the foundation's "economic assessment" of the mine and its impact on the region.

It concluded: "In the Commission's opinion the analysis is not rigorous and the assertions made are not necessarily supported by the evidence presented."

But research foundation chief executive Wej Paradice is standing by the assessment, which was overseen by director of research Andrew Searles.

Dr Paradice said that after reading the commission's report on Bickham he believed the panel had "not really assessed our report with the level of rigour it deserves".

Dr Paradice said the commission challenged Bickham's employment predictions but accepted evidence from the horse industry, apparently without question.

"What is the basis for their claim that the employment is likely to be substantially less and relatively little from the local area?" Dr Paradice said.

"It's a regional model not a local model. It's not something we claimed anyway," he said.

"They say the potential loss of employment [from the equine industry because of Bickham] could be substantial, but where is the evidence?"

Dr Paradice said it was important to the foundation that its "reputation for doing good work remains unsullied".

"Given the reputation of the foundation on those issues I am looking at whether we do write to the commission."

The Bickham assessment used the foundation's well-regarded "input-output" economic modelling, which built on a large data-base of real-life Hunter business and employment outcomes, he said.

The only information that Bickham supplied was its estimate of the number of mineworkers, which the foundation had reason to believe would be accurate. Population statistics, which the commission had said were "not investigated rigorously", had all come from the 2006 census or from other government sources.

A spokeswoman for the commission did not respond to criticism and said that "everything" it wanted to say was in the Bickham report, available from: www.pac.nsw.gov.au