The Democratic Party of Wisconsin blasted oil billionaire David Koch on Monday for supporting Republican Gov. Scott Walker in his fight against public unions.

"I think I speak for most Wisconsinites when I say to David Koch, 'Get out of Wisconsin and take Scott Walker's dangerous agenda with you,'" Democratic Party of Wisconsin Chair Mike Tate said.

In a rare interview with the Palm Beach Post, Koch described Walker as "impressive" and "courageous." He said his conservative group Americans for Prosperity was hard at work in Wisconsin.

"We've spent a lot of money in Wisconsin," Koch said. "We're going to spend more."

Walker and Republican lawmakers pushed to curb the collective-bargaining rights of public employees earlier this year, eventually passing the highly controversial legislation using a parliamentary maneuver.

The attack on collective-bargaining rights set off unprecedented recall campaigns against Republican and Democratic Wisconsin state senators. Democrats ended up gaining two seats in the Senate after defeating incumbent Republicans. Walker now faces a recall election himself.

Koch said restricting collective-bargaining rights was "critically important" and warned there would be "no stopping union power" if Walker is ousted from office.

"This disturbing interview shows a man in David Koch who believes that because of his wealth, he should be able to dictate what happens in a place he hopes to convert into a plantation state for his low-wage, low-benefits, no-rights companies. Wisconsin cannot let David Koch or Scott Walker buy Wisconsin and break our middle class," Tate said.