Story highlights Rep. Trent Franks, an Arizona Republican, stepped down effective Friday

The House Ethics panel was investigating whether he had sexually harassed his staff

Washington (CNN) A special election to fill the seat vacated by Arizona Republican Rep. Trent Franks will be held next year, with a primary February 27 and the general election April 24.

Arizona Gov. Doug Ducey announced the election dates Monday morning in an official state proclamation.

Franks said in a statement Thursday night he would resign from Congress after the House Ethics Committee said it would investigate allegations of sexual harrassment against him.

The House Ethics Committee announced earlier Thursday that it will investigate Franks to determine if he engaged in "conduct that constitutes sexual harassment and/or retaliation for opposing sexual harassment."

In his statement , Franks acknowledged he made staffers "uncomfortable" and that he discussed fertility issues and surrogacy with two female staffers, but denied having ever "physically intimidated, coerced, or had, or attempted to have, any sexual contact with any member of my congressional staff."