Republican National Committee Chairman Michael Steele said the White House's explanation of how Rep. Joe Sestak (D-Pa.) was offered an executive branch board position "raises more questions."

"What was Bill Clinton authorized to offer?" Steele asked in a statement. "Did President Obama sign off on this conversation before it took place?"

White House Counsel Bob Bauer addressed the controversy in a two-page memo released Friday. The memo confirmed reports that former President Bill Clinton spoke to Sestak at the request of White House Chief of Staff Rahm Emanuel about dropping out of the race against Sen. Arlen Specter (D-Pa.).

Steele called the memo "unsubstantiated."

"Now, more than ever, it is clear that this White House is not capable of policing itself and needs to open itself to an independent investigation," Steele said.

Senate Judiciary Republicans have asked the White House to appoint a special prosecutor to investigate the matter. The memo did not address the Republicans’ request.

—Sam Youngman and Walter Alarkon contributed to this post.

Cross-posted from the Ballot Box