DES MOINES, Iowa - An Iowa Senate ethics panel has voted to appoint a special investigator to review charges that a state senator took payments from a presidential campaign.

The panel voted Wednesday to ask the chief justice of the state Supreme Court to appoint an investigator to review the complaint against Republican Sen. Kent Sorenson, of Milo.

An Iowa campaign adviser to U.S. Rep. Michele Bachmann's 2012 presidential campaign has provided the committee with an affidavit saying the Minnesota congresswoman approved a plan to indirectly pay Sorenson for campaign work.

Iowa Senate ethics rules bar paid employment with political campaigns.

Sorenson says he was never paid directly or indirectly. He has offered an affidavit from an attorney who audited his bank statements and says there is no evidence of the alleged payments.