“The Fake News photoshopped pictures of Melania, then propelled conspiracy theories that it’s actually not her by my side in Alabama and other places,” he tweeted, without providing evidence.
“They are only getting more deranged with time!”
The US president’s outburst came after some social media users suggested the First Lady looked different during the couple’s recent visit to Alabama to pay their respects to 23 victims who died in a tornado.
“I see unconvincing Melania stunt-double is back,” one Twitter user wrote over the weekend, alongside an image showing Ms Trump in dark sunglasses and holding the president’s hand.
Claims Ms Trump has used a body double first surfaced in late 2017 during an appearance at a press conference alongside her husband. She again partially obscured her face by wearing large, dark sunglasses.
On Tuesday, Ms Trump issued an angry response through her spokesperson to ABC, after a segment on daytime talk show The View made fun of the ongoing conspiracy.
“Some people think the first lady is using an impostor to stand in for her,” co-host Joy Behar said. “You mean there are two women who have to pretend they’re listening to (President Trump)?”
Stephanie Grisham, Ms Trump’s representative, responded in an email to ABC it was “sad” the female presenters “spend so much time attacking another woman, whose only goal is to help children”.
The unfounded rumour had echoes of another conspiracy involving Ms Trump last summer, after she failed to make a public appearance in more than three weeks.
Her temporary disappearance sparked a deluge of rumours and theories, until the White House announced she had been recovering from surgery.
“The Fake News Media has been so unfair, and vicious, to my wife and our great First Lady, Melania,” he tweeted at the time. ”During her recovery from surgery they reported everything from near death, to facelift, to left the W.H. (and me) for N.Y. or Virginia, to abuse. All Fake, she is doing really well!”