Ex-WH Press Sec. Claims Melania Aide Made 'Beverly Hillbillies' Crack About Trumps

Come and listen to a story 'bout a man named Don

A poor President who didn't know right from wrong

And when his kids asked to meet the Royal Queen

His staff stepped in so they never would be seen

Stephanie Grisham -- the former White House press secretary under Donald Trump best known for holding zero press briefings -- is saying plenty about him now, and like many other of his former employees ... it ain't positive.

Grisham's got a new book coming out this week, and in it, she details her experiences working in Trump's White House and dealing with his family ... including when they went to visit The Queen in June 2019.

TMZ's obtained an excerpt from the book -- titled "I'll Take Your Questions Now: What I Saw in the Trump White House" -- in which she says the trip to the U.K. for dinner with Queen Elizabeth royally excited the Trump children.

In fact, Grisham writes ... "It was the only trip in all four years that every single member of the family expected to attend."

Problem was, according to Grisham, the Trump fam also wanted royal service along the way ... including getting to ride on Air Force One, and spots at the Queen's official state dinner table for Don Jr.'s girlfriend, Kimberly Guilfoyle, and Tiffany's boyfriend too.

Grisham says this didn't fly with Melania's chief of staff, Lindsay Reynolds, whom she claims was concerned the Trump kids would ruin the trip simply so they could get attention.

Grisham claims Reynolds told her, "We are going to look like the Beverly Hillbillies," adding ... "We'll be an embarrassment to the whole country."

The allegations get even juicier from there -- with plenty of smoke for Ivanka and Jared too -- so check out the full excerpt for more.

It should be noted, Grisham describes Trump's White House in her book as "a clown car on fire running at full speed into a warehouse full of fireworks" ... so you know what else to expect.

Ex-President Trump, through his spokesperson, is already refuting Grisham's claims, telling TMZ ... "Stephanie didn't have what it takes and that was obvious from the beginning. She became very angry and bitter after her break up and as time went on she was seldom relied upon, or even thought about."