Gilbert Burnham said in the Lancet medical journal in 2006 that 650,000 civilians had died since 2003 - a figure far higher than other estimates.
A polling association in the US said Dr Burnham had refused to supply "basic facts" for its inquiry into his work.
It did not comment on the accuracy of his conclusion.
The American Association for Public Opinion Research (AAPOR)began investigating Dr Burnham's work .
Reproducibility is of course one of the key parts of the scientific method. They should be begging for people to review their work, not blocking them.