An investigation by the Yavapai County Attorney has found there's enough evidence to show Arizona Attorney General Tom Horne violated campaign finance laws during his 2010 run for office.

County Attorney Sheila Polk ordered Horne to return nearly $400,000 to donors and amend his campaign finance reports or she would also seek stiff civil penalties.

Thursday's announcement marks the second time a prosecutor alleged Horne violated campaign laws. Horne's lawyers sidetracked the earlier civil action by Maricopa County Attorney Bill Montgomery by arguing the secretary of state's office followed the wrong procedure when it referred the case to Montgomery.

Polk found reasonable cause to believe Horne and aide Kathleen Winn worked together to raise about $500,000 through an outside group she chaired.

Horne and Winn have denied the allegations.