Newt Gingrich pounced on challenger Ron Paul today for controversial newsletters containing racist, anti-gay slurs.

The newsletters published by the Texas congressman for years contained hateful language about blacks and gays and comments describing the Rev. Martin Luther King Jr. as a "world class adulterer."

Gingrich today called on Paul to defend the racist sentiments.

"I think that Congressman Paul has to explain his own situation and how he could have had a decade of newsletters that had his name on it that he apparently wasn't aware of," Gingrich said.

Paul has denied being aware of the racist language.

"I didn't write them. I disavow them. That's it," Paul told CNN recently, although his past statements promoting the newsletter appear to contradict them.

This isn't the first time Gingrich and Paul have butted heads. The rivalry between the two goes back to 1995, when then-House Speaker Newt Gingrich worked unsuccessfully to deny Paul a Texas House seat in a bitter primary battle that pitted Paul against a Gingrich-backed, Democrat-turned-Republican opponent.

"He orchestrated a million-dollar campaign to keep me out of Congress," Paul told the Houston Chronicle at the time.

Paul last week unveiled an ad attacking Gingrich for being a serial hypocrite and for building his wealth through questionable lobbying efforts.

"He's been on a lot of different sides on all the issues," Paul told ABC News' Jon Karl. "He may be the opposite of what I've been doing for 30 years. My positions haven't changed all that much."

ABC News' Jason Volack contributed to this report.