Banks and credit unions are squaring off on the social media front over a Depression-era law that exempts credit unions from federal income taxes.

The Twitter wars stem from the American Bankers Association's current crusade to persuade Congress to repeal their rivals' tax breaks. Under current law, it is the credit unions' cooperative structure that exempts them from federal income taxes.

The ABA unveiled a print and radio ad campaign in March opposing the exemption. It extended the campaign to Twitter in late July when it launched an account dubbed @ItsTime2Pay. The Twitter handle has been pushing out a steady stream of dispatches ever since urging bankers and the public to help end the tax exemption.

"The avg. US family pays more in federal income taxes than the entire $1 trillion #creditunion industry," the ABA wrote on Friday.

Credit unions are fighting back through their own industry group. "#ItsTime2Pay is asking YOU to pay," the Credit Union National Association (@CUNAadvocacy) wrote Friday. " W/o #creditunions, bank fees & costs would only rise further = more $ out of your pocket." Credit union supporters have also gotten involved, using the hashtag #DontTaxMyCU.

The creator of Bank Transfer Day, which encourages bank customers to close their bank accounts and open new ones at credit unions, has also thrown her hat into the ring. "The #ABA sinks to a new low & tells 96 million Americans- "@ItsTime2Pay!" Kristen Chistian wrote earlier this week.

The 96 million figure appears to be a bit of a stretch. As of Friday afternoon, the ABA's @ItsTime2Pay Twitter handle had only 152 followers.