David Letterman jokingly told Lauren Conrad what he really thinks about The Hills during his Monday night show.

When questioning Conrad, 22, about her former feud with Heidi Montag, he said: “That raises the question…maybe you’re the problem, you think?”

(The girls reunited at a dinner party following Conrad’s spring runway show a few weeks ago.)

Letterman also dissed Spencer Pratt - again.

“Now that Spencer, what a weasel,” Letterman said. “He’s just the worst, that guy… what’s his deal?”

Admitted Conrad: “I don’t know.”

Letterman complained of his last interview with Pratt, saying, “He had some big giant watch on….”

“He was probably checking his 15 minutes!” shot back Conrad.

Brody Jenner didn’t escape the barbs either.

“What does he do?” Letterman quizzed.

“Well, he, um, he’s very good-looking,” Conrad said. “And he’s been on The Hills, he works on a jewelry line, he has a clothing line, he has a show, Bromance, he helped produce….”

Said Letterman: “If there was no television, this guy would be living in a tree. I don’t know what that means!”

Conrad stopped by the show to talk about her work for Mark, a subsidiary of Avon. The Hills star is attending the Avon Foundation Hope Honors Gala Wednesday night to celebrate her help in raising $250,000 to donate to seven different organizations to educate and prevent partner violence against young women.

Later Monday night, Conrad was spotted out to dinner in NYC’s meatpacking district with her actor beau, Kyle Howard.

(source)