Lahren, a host on Fox News' subscription service Fox Nation, made the remark during the opening stages of Wednesday's Democratic debate, calling Harris out for her past relationship with former San Francisco Mayor Willie Brown in the mid-1990s.
"Kamala did you fight for ideals or did you sleep your way to the top with Willie Brown," Lahren tweeted.
She later followed up on the accusation just hours later tweeting, "I didn't make this up.... The truth hurts," linking to a USA TODAY article about Brown's comments on his previous relationship with Harris.
Kamala did you fight for ideals or did you sleep your way to the top with Willie Brown?— Tomi Lahren (@TomiLahren) August 1, 2019
Brown said he had a relationship with Harris when he was speaker of the California Assembly, "more than 20 years ago."
Lahren received backlash about the comment, including recoil from fellow Fox Nation host Britt McHenry, who questioned if Lahren had "any idea how damaging this is to women who’ve actually been sexually harassed, assaulted or demeaned in the workplace."
"How much this weakens our own gender, regardless of partisanship," McHenry said, adding, "My goodness."
Lahren followed up her message with an apology.
"I apologize for my comment on Kamala’s personal relationship. It was the wrong choice of words. There are many other things to take her to task for and I will stick to those," she wrote.
Fox News spokesperson Carly Shanahan declined to comment further on the situation, pointing to Lahren's tweet as the statement.
I apologize for my comment on Kamala’s personal relationship. It was the wrong choice of words. There are many other things to take her to task for and I will stick to those.— Tomi Lahren (@TomiLahren) August 1, 2019
This isn't the first time Lahren has made waves for her choice of words on social media.
The TV host started a Twitter feud with rapper Cardi B in early January after mocking her as, "the latest genius political mind to endorse the Democrats."
"Leave me alone I will dog walk you," Cardi quipped back.
"I’m sure you would," Lahren replied. "Still doesn’t make your political rambling any less moronic," adding the hashtag #BuildThatWall.
Contributing: Associated Press, Kim Willis
This article originally appeared on USA TODAY: Kamala Harris earns apology from Tomi Lahren: 'Wrong choice of words'