Vice President Joe Biden had tough words for lawmakers who’ve tried to limit voting rights Tuesday, warning that they may ruin their chances of winning minority voters.

“If they keep this up you can be assured, minorities of all stripes will never vote for anyone who makes it more difficult for them to exercise right to vote,” Biden said in a speech at the annual gala for the Joint Center for Political and Economic Studies.

“To me it is the most immoral, callous thing that can be done, the idea of making it more difficult to vote,” he said, without specifically naming Republicans, but appearing to make a thinly veiled warning to the party that has been behind the vast majority of voter suppression efforts in recent years.

He lamented the recent debate over Section 5 of the Voting Rights Act, pointing out that one-time Dixiecrat Strom Thurmond eventually supported the measure in his career.

Biden called it “an irony” that “just a few years after electing the first African American president in the history of the United States of America,” more than 80% of states in the U.S. introduced or passed 180 laws that “make it more difficult for minorities to vote.”

Read more at MSNBC.