An immigration reform group says the Southern Poverty Law Center legal firm is violating federal tax rules for non-profits by acting “as a campaign operation for one political party.”

The Immigration Law Reform Institute, which is an affiliate of the Federation for American Immigration Reform, is now preparing a legal claim to pressure the Internal Revenue Service to end the SPLC’s non-profit status. If that happens, donors wouldn’t get tax deductions for giving to the group.

“This document with exhibits runs over 100 pages, and spells out in laborious detail how the SPLC operates as a campaign operation for one political party and nothing more. For a huge range of reasons, the SPLC deserves to lose its tax status as a 501(c)(3) operation,” said a Nov. 22 statement from FAIR.

“FAIR has argued for years that the SPLC is not a legitimate charity – it is a partisan organization engaged in illegal political activity,” said the statement.

FAIR has long clashed with SPLC, while the SPLC has long accused FAIR of being a supposed “hate group.” For example, in October 2015, the SPLC posted a statement saying “The anti-immigrant hate group Federation for American Immigration Reform (FAIR) will be holding its latest ‘border tour’ on October 30 and 31 in McAllen, Texas.”

“The SPLC continues to state that FAIR has ties to people it has no ties to, is interested in things it’s not interested in, and is working for ends it’s not working toward,” said Dan Stein, FAIR’s president. “The SPLC’s attacks have been refuted and effectively dismissed by the media, government agencies, and others who continue to rely on FAIR for information and commentary,” Stein said in his statement.

The SPLC’s role as a charity has been the subject of much criticism. The group’s research was used by a gunman to guide his attack on the Family Research Council, and it was snubbed by the FBI.

The SPLC did not respond to Breitbart News.