Pippi Longstocking Porno -- Movie Studio Cracks Down ... Stop Using 14-YEAR-OLD to Promote Sex Tape

Images of a 14-year-old Pippi Longstocking have no business on a Pippi Longstocking sex tape website ... and now a major Hollywood movie studio is gearing up for war, TMZ has learned.

We know ... Columbia Pictures, the studio behind "The New Adventures of Pippi Longstocking," learned that multiple websites associated with the Tami Erin sex tape are using images from the 1988 movie to promote the XXX footage.

Obviously, that ain't sitting well with Columbia ... so lawyers stepped in and fired off an email, warning the websites to take down shots of the freckle-faced red head girl immediately, or face a big, fat lawsuit.

The sites complied for the most part -- removing images of the DVD as well as links to purchase it -- but it still includes many Pippi references, as well as a screenshot from the original movie (in which Tami is 14).

We've learned ... one of the XXX sites responded by adding a disclaimer on the home page, saying the sex tape is not sponsored, endorsed by or affiliated with the studio.

So far, it's unclear how Columbia feels about the compromise.

FYI, you won't believe how popular the Pippi porno websites are -- we're told they both average over 200k views per day. Curiously, the biggest chunk of traffic comes from Sweden.

Bork, bork, bork!