One of the ads, erected this week in Times Square, depicts a smiling Trump gesturing toward the numbers of New Yorkers and Americans who have so far died from COVID-19. In an adjacent ad, her husband is pictured along with the quote, "[New Yorkers] are going to suffer and that's their problem," attributed to him.
Their lawyer, Marc Kasowitz, called the ads "false, malicious and defamatory" in a cease-and-desist letter the Lincoln Project posted on Twitter Friday.
"Of course, Mr. Kushner never made any such statement, Ms. Trump never made any such gesture, and the Lincoln Project's representations that they did are an outrageous and shameful libel," the letter said. "If these billboard ads are not immediately removed, we will sue you for what will doubtless be enormous compensatory and punitive damages."
An hour after sharing the letter, the Lincoln Project responded that the "billboards will stay up" and called the White House advisers "entitled, out-of-touch bullies."
"The level of indignant outrage Jared Kushner and Ivanka Trump have shown towards The Lincoln Project for exposing their indifference for the more than 223,000 people who have lost their lives due to their reckless mismanagement of COVID-19 is comical," the group said in a statement.
The quote attributed to Kushner was pulled from a September Vanity Fair article. In it, a source alleged that Kushner said that New York Gov. Andrew Cuomo "didn't pound the phones hard enough to get PPE for his state…. His people are going to suffer and that's their problem."
On Thursday, the Lincoln Project posted photos of the new billboards on Twitter, saying, "It's a good morning in Times Square for Ivanka and Jared."
In another post, the group said, "There must be accountability for the lying and deaths -- this is just the start."
ABC News reached out to Kasowitz for comment.