EXCLUSIVE

Jason London crapped himself in the back seat of a cop car Sunday morning ... minutes after the "Dazed & Confused" actor was punched in the face in a bar fight ... this according to a police report obtained by TMZ.

Here's what the report says ...

Cops were called to the Martini Ranch bar in Scottsdale, Arizona at 1:42 AM on Sunday morning after getting a call about a man who was bleeding on the street.

When officers arrived to the scene ... they found Jason nursing a swollen eye. Cops spoke to a bouncer who told them Jason had been inside the club, walked by him and sneezed on him. The bouncer asked for an apology, and Jason allegedly punched him in the face.

40-year-old Jason was thrown out of the bar kicking and screaming and in the process he was beaten up.

Paramedics arrived to the scene to treat London, but cops say the actor got aggressive with the responders and shoved some of them. Cops say one of the officers was forced to deliver a knee strike to London's right thigh so they could seat him on the ground. London later called one of the officers a "f**king hillbilly."

Jason was eventually arrested for disorderly conduct/fighting and assault.

On his way to the police station ... Jason uttered a homophobic slur to the cops ... saying, "Guess what fa**ot? I f***ing love this. I f***ing own you guys so hard. I'm rich and I'm a motherf***ing famous actor! F***ing look me up, bitch."

Jason continued ... "It smells like s**t in your car and your breath smells like diarrhea." According to the police report, Jason then leaned to the left and crapped in his pants. Jason then said, "I told you I'm happy as s**t."

The next day, cops say they spoke with Jason's wife Sofia who told them ... "I know he's an a**hole when he drinks."

Cops say Sofia also told them she had spoken with Jason ... and he had no recollection of the incident.

1:50 PM PT -- Jason just tweeted about the story ... saying the police report is a "total f*cking lie."

Jason explains, "I got jumped by three 250 pound bouncers. They knocked me out and beat me for several minutes."

"I would never say or do the crap they are reporting. Have faith in me. The truth will come out and you will see."