Vitter, R-La., ranking member of the Senate Environment and Public Works Committee, asked Tribal Affairs Assistant Administrator for the Environmental Protection Agency Michelle DePass for information about what support she's received from the Ford Foundation, her previous employer.
"If you received benefits from the Ford Foundation that you used to execute your official duties, that is sufficient to consider your actions inconsistent with your duty as a federal employee," Vitter said in a statement.
Vitter led a boycott last week over the nomination of former Assistant EPA Administrator Gina McCarthy to take over the agency. Republicans skipped a vote last week, saying they were concerned about transparency at the EPA.
McCarthy was approved in a vote by a Democrat-controlled Senate committee vote along party lines, 10-8. Her nomination heads to the full Senate for confirmation.
2014: The Year in Music [PHOTOS]