The Iowa Senate Ethics Committee has asked the state's chief Supreme Court justice to appoint a special investigator to probe an alleged ethics violation by state Sen. Kent Sorenson, who is accused of accepting payments from U.S. Rep. Michele Bachmann's presidential campaign in 2012.

The panel reviewed an affidavit from former Bachmann chief of staff Andy Parrish. He said Bachmann approved a plan to indirectly pay Sorenson $7,500 a month to work on her campaign.

Parrish's affidavit included copies of emails between him and other staff members discussing plans to use a company run by Bachmann's then-national political director, Guy Short, to funnel payments to Sorenson.

The alleged payments could violate an Iowa Senate ethics ban that prohibits members from accepting payments for work on political campaigns.

Sorenson denied any wrongdoing.

"I was never paid directly or indirectly by Michele PAC or the Bachmann campaign," read a statement he provided to the Senate ethics committee Wednesday. "Andy Parrish, a gentleman who was removed from the employ of the Bachmann offices due to my sharing of information with the congresswoman, is the only person to attempt to provide contrary information."

Another former Bachmann staff member, Peter Waldron, filed the complaint against Sorenson, alleging that the Iowa Republican knowingly violated Iowa Senate rules by accepting payment for working on the campaign.