8:20 AM PT -- Stephanie Grisham has elaborated on her initial tweet by releasing a statement, saying, "Like it or not, she is the First Lady and this is the White House. It's disrespectful and disgusting to portray her this way simply because of politics."

She continued, "These kinds of vulgar attacks only further the divisiveness and bias in our country - it needs to stop."

T.I. is going directly after President Trump and the First Lady with a salacious video of a Melania look-alike stripping in the Oval Office ... for T.I.!!!

Melania's office is firing back at Tip for the video he released over the weekend ... it shows him in the Oval, kicking back smoking a cigar. After Trump leaves the White House, "Melania" walks in wearing nothing but her infamous "I Really Don't Care" jacket ... but only for a few seconds.

Suddenly, she's naked and on the Presidential desk giving T.I. full view of ... everything.

T.I. was clearly trying to draw the ire of POTUS ... slapping the caption "Dear 45, I ain't Kanye" on the video.

Melania's rep Stephanie Grisham tweeted, "How is this acceptable? #disgusting #boycottT.I."

No response yet from T.I. ... but seems like mission accomplished for him.