Sen. Claire McCaskill, D-Mo., has called for a crackdown on offshore tax havens, but her husband has invested $1 million in a hedge fund with connections to the Cayman Islands.

Joseph Shepard began investing in Matrix Capital Management, a hedge fund registered in the Cayman Islands, four years after McCaskill co-sponsored a bill targeting tax havens.

Shepard's investments have earned him somewhere between $230,000 and $2.1 million in income, according to The Kansas City Star.

Shepard, who files his taxes separately from his wife, declined to comment to the newspaper.

A spokesperson for her re-election campaign, Meira Bernstein, told the Kansas City Star that McCaskill "does not make decisions on public policy based on what's best for her husband; she makes decisions based on what is best for the people of Missouri. That's why she voted against the recent tax bill that primarily benefited large corporations and the wealthy. And it's why she supported the Stop Tax Haven Abuse Act."

The bill, which did not pass, said that tax havens are "engaged in economic warfare against the United States, and honest, hardworking Americans."