The intensifying debate over the Export-Import Bank’s future spilled over to Twitter yesterday after a top official with the U.S. Chamber of Commerce took to the social media site to criticize Rep. Justin Amash, R-Mich., for his opposition to the contested agency.

The U.S. Chamber of Commerce is one of the bank’s most vocal supporters, and on Sunday night, news broke that the group would be putting big bucks behind an advertising campaign designed to drum up support for Ex-Im’s reauthorization.

The $1 million multimedia blitz launched today across 10 states, with the Chamber focused on reaching Republican lawmakers who are on the fence about extending Ex-Im’s life.

Shortly after The Wall Street Journal published an article detailing the campaign, Amash took to his Twitter account to criticize the Chamber’s push.

The Michigan Republican’s comments caught the attention of Rob Engstrom, senior vice president and national political director at the Chamber, who called Amash’s representation of Michigan “shameful.”

Amash is one of 87 Republicans who have come out against Ex-Im’s reauthorization. He, along with the bank’s opponents, believe the 80-year-old agency serves as an engine of cronyism and corporate welfare.

However, the bank’s supporters, such as the Chamber, argue Ex-Im helps small businesses compete in the global market and creates jobs in the U.S.

Ex-Im’s charter expires June 30, and debate about its future is ramping up between policymakers on Capitol Hill and outside groups. While the Chamber is advocating for the bank’s reauthorization, Heritage Action for America,—the lobbying arm of The Heritage Foundation—Freedom Partners Chamber of Commerce and Americans for Prosperity have been pushing for Ex-Im’s end.