Jaime Pressly -- Estella Warren Messed With the Wrong Posse!

Jaime Pressly says Estella Warren's purse-snatching episode was NO accident, and she's warning the actress to never do it again ... OR ELSE.

Jaime was out in L.A. Tuesday and unloaded about her weekend confrontation in a nightclub with Estella. Jaime says her assistant's clutch and phone were stolen, and claims she caught EW red-handed.

Not only that, Jaime says Estella's pseudo apology -- where she claims it was a simple misunderstanding -- is a giant crock.

You gotta see Jaime's explanation of the whole caper, and best of all ... her bold warning to Estella.