The request comes a day after a report that companies tied to McCaskill's family benefited from nearly $40 million in federal funds since she was elected.
The extent to which McCaskill's family actually profited off of the funds, which Akin's campaign is trying to make an issue, is mostly unclear. Most of the $40 million was distributed by the U.S. Department of Agriculture specifically to be spent on low-income housing, and specifically not profit.
"This conjecture and speculation on my part," Akin adviser Rick Tyler admitted, but said his campaign believes the only way to know exactly how much McCaskill's family benefited is if her husband, Joseph Sheapard, releases years of tax returns.
When Akin's campaign was asked whether the Akins would release their own tax returns, Tyler said Akin has not released his own returns, but said he and his wife Lulli "would be glad to disclose" returns for the same period of time if McCaskill and her husband do the same.
So far, McCaskill's campaign said on Wedensday, McCaskill is the only candidate in the Senate race to release tax returns.
"Todd Akin's repeated attacks against Claire's family are a desperate, baseless attempt to distract from his extreme record that would be very painful for Missouri's families," said McCaskill spokeswoman Caitlin Legacki.