"I have the direct number to White House but I don't really want to call him there because Melania is there, and I don't really want to cause any kind of jealousy or something like that because I'm basically first Trump wife, OK? I'm first lady, OK?" Ivana said in an interview to ABC News.
The first lady, Melania Trump, was quick to respond.
She released a statement saying she had made the White House a home for Trump and their son Barron, and that she planned to use her title to "help children, not sell books."
"Mrs Trump has made the White House a home for Barron and the president," the statement said.
"She loves living in Washington, DC, and is honored by her role as first lady of the United States.
"She plans to use her title and role to help children, not sell books," it added.
"There is clearly no substance to this statement from an ex, this is unfortunately only attention-seeking and self-serving noise," she added.
Ivana Trump is the mother of Trump's three eldest children: Donald Trump Junior, Ivanka, and Eric.
Trump has one other child, Tiffany, with his second wife, the actress Marla Maples.