Business Insider previously reported that Barry has never spoken negatively about her brother in public, and the comments were recorded in conversation with the president's niece, whose critical tell-all about him was published in July.
"The president of the US is calling everything a hoax," Pelosi said. "He's called the virus a hoax for a while, he's called Russian interference in our elections a hoax. He calls everything a hoax. Which is just a projection of what he is – a hoax."
Barry's comments are "just further evidence of inauthenticity and his lack of integrity," Pelosi said.
"Every day it's something else, who cares," Trump said in a statement dismissing his sister's comments to Business Insider. "I miss my brother, and I'll continue to work hard for the American people. Not everyone agrees, but the results are obvious. Our country will soon be stronger than ever before."
Top associates from the Trump administration and campaign appeared in broadcast interviews on Sunday to defend the president against Barry's comments, which White House chief of staff Mark Meadows said Sunday on Fox News said were "to promote an agenda."