Former Georgia Gov. Roy Barnes (D) unleashed a hard-hitting attack ad Tuesday against former Rep. Nathan Deal (R) in the state's race for governor.

Barnes is seizing on the recent flap over Deal's tax returns, which the Republican released last week amid pressure from his opponent. 

Deal resigned his House seat in March to focus on his campaign for governor, but the retirement also came after the Office of Congressional Ethics said he had improperly described income from his family's salvage business.  

The 30-second spot from Barnes charges that "secrets are hidden in the details" of Deal's returns. 

"That's why he resigned from Congress at midnight," the ad's narrator says. "Nathan Deal — too corrupt, even for Congress."

Deal narrowly won a runoff last month over Karen Handel for the right to take on Barnes. Deal received some prominent backing from two rumored Republican presidential hopefuls — former House Speaker Newt Gingrich and former Arkansas Gov. Mike Huckabee.

(h/t: Atlanta Journal Constitution)

—Sean Miller contributed to this post.