United States First Lady Melania Trump has engaged in a war of words with President Donald Trump’s first wife, Ivana Trump, after the latter claimed she was the original First Lady.

Ivana, 68, was promoting her tell-all memoir, Raising Trump, during an interview with Good Morning America when she said she had a direct line to her former husband.

“I have the direct number to White House,” she said.

“But I’m not really going to call him there because Melania is there, and I don’t want to cause any kind of jealousy or something like that, because I’m basically first Trump wife, OK? I’m First Lady, OK?”

Melania, 47, responded to Ivana’s claims via her spokesperson, Stephanie Grisham, who issued a scathing statement about Ivana’s intentions.

“Mrs Trump has made the White House a home for Barron and the President. She loves living in Washington, D.C., and is honoured by her role as First Lady of the United States,” Ms Grisham said.

“She plans to use her title and role to help children, not sell books. There is clearly no substance to this statement from an ex. Unfortunately, only attention-seeking and self-serving noise.”

Ivana, a Czech-born former model, was married to the President for 15 years and is the mother to his three elder children, Ivanka, Donald Jr and Eric.

Meanwhile, Melania, a Slovenia-born former model, wed Mr Trump in 2005 and is mother to their 11-year-old son, Barron.

Ivana’s book details her tumultuous relationship with the real estate mogul-turned-president, and sees her claim credit for raising their kids.

“When Donald started to campaign, he was going on the debates, and [the kids] were going with him to rallies, people came to know them,” she told Time magazine this week.

“On the street and in the airport, total strangers were coming to me and they’d say, ‘Ivana, how did you do it, to raise such a fabulous kid?'”

While she may not possess the official title, Ivana argued she would be an excellent First Lady.

“Could I straighten out the White House in 14 days? Of course,” she told Time.

“Can I go and give the speech without a teleprompter for 45 minutes? Of course. Can I entertain? Of course I can entertain. But it is just not something I would like to do.”

Melania was not the only Trump wife to have been targeted by Ivana – she also took a swipe at his second wife, Marla Maples, 53, who is mother to his daughter, Tiffany, calling her “the showgirl”.