First lady Melania Trump has thanked Chelsea Clinton, the daughter of her husband's former rival for the presidency, on Twitter for coming to the defense of the Trumps' youngest son.

Chelsea Clinton criticized the Daily Caller, a conservative news website, for publishing an article by its entertainment reporter criticizing the clothes of 11-year-old Barron Trump.

The reporter wrote it was time the president's son "starts dressing the part" and ditches his T-shirts and shorts in favor of a blazer, shirt and tie with combed hair when in public.

The article drew widespread scorn, notably from Chelsea Clinton, whose appearance was often picked over by news outlets while she was a child growing up in the White House and her father, Bill Clinton, was president in the 1990s.

"It's high time the media & everyone leave Barron Trump alone & let him have the private childhood he deserves," Clinton wrote on Twitter on Monday, referring to the article.

Clinton has long been friendly with Barron's sister, Ivanka Trump, despite President Donald Trump's attacks on Clinton's mother during last year's presidential campaign when he began calling her "Crooked Hillary."

The younger Clinton's defense was noticed by the first lady.

"Thank you @ChelseaClinton - so important to support all of our children in being themselves!" Melania Trump tweeted late on Tuesday, adding the hash tag: "#StopChildhoodBullying."