Gary from 'Teen Mom' -- 'Amber Is Sluttish'

1/2/2011 12:00 PM PST BY TMZ STAFF
"Teen Mom" baby daddy Gary Shirley has a lot to learn about relationships -- like rule #1 ... don't call your baby mama a slut while on the phone with her cousin.


In an audio recording from December obtained TMZ, Gary is heard on the phone with Krystal,  Amber Portwood's cousin. Gary explains to Krystal he kind of has a crush on her ... pointing out, "You've got things that Amber don't ... like a job."

Then Gary drops a real gem and tells Krystal, "Amber is sluttish. You've been with six dudes, Amber's been with f**king a million."

The topper ... dude actually tries to convince Krystal to come to his place by saying, "If you ever want to piss off Amber, let me know."

Mission accomplished.