"I will be referring this matter for investigation by the Department of Justice if you once again refuse to comply," Nunes wrote in a letter.
"The investigation is particularly focused on the guidelines that appeared on a whistleblower complaint submission form that was changed — after the submission of the whistleblower complaint — to eliminate language excluding hearsay information," Nunes added.
According to Fox News, House Intelligence Committee Republicans are investigating Atkinson's "unusual handling" of the complaint, which was the key component of the Democrats' impeachment effort against President Trump.