A day after the interchange amendment passed, Sen. Dick Durbin (D-Ill.) sent a missive to two credit-union and small-bank associations asking them to change tactics and support the measure.

The letter follows an intense lobbying battle between retailers and banks over swipe fee legislation that gives the Federal Reserve more power to negotiate the rates that banks require merchants to pay when customers use debit and credit cards. The legislation also allows merchants to negotiate discounts with consumers when using certain payment cards.

The Credit Union National Association and the Independent Community Bankers of America both vigorously opposed the amendment to the financial services reform bill. CUNA took the unusual step making it a key vote in their Member ratings.

Durbin wrote the two trade groups Thursday, saying that they have been misrepresenting his legislation.

“Your associations have urged your member institutions to oppose my amendments using a variety of scare tactics,” Durbin wrote. “I will tell you what I have told small banks and credit unions in my home state of Illinois — that my amendment does not disadvantage small banks and credit unions, and in fact goes to great lengths to protect their ability to successfully compete with big Banks in offering payment cards to consumers.”

CUNA President Dan Mica said he appreciated Durbin’s interest in the issue.

“I intend to be back in touch with him and his staff to try to work this out,” Mica said in a statement. “CUNA is charged with representing the best interests of credit unions and their 92 million members; Sen. Durbin’s letter indicates a concern for credit unions and developing sound public policy toward them.”

“We take that at face value and think that, together, we can find a way to ensure our mutual concerns are addressed,” he added.

ICBA’s Steve Verdier did not immediately respond to a request for comment.