9:45 AM PT -- TMZ obtained the uncensored video of Brian Littrell and the beachgoer going at it, and he does NOT use an epithet. Check it out here ... Brian did curse, but no slurs were hurled.

Brian Littrell from the Backstreet Boys is in hot water today after a video reportedly appears to show Littrell calling someone the homophobic f-slur.

In the video, obtained by local outlet WMBB, Littrell confronts a beachgoer identified as Kyle Gallagher. During the altercation, PEOPLE reports Littrell appears to say, "You want to be gay? Want to be a f*****?"

And get this ... Littrell submitted the video himself because he thought it would help his case against Gallagher! But Littrell's attempt to press criminal charges failed ... big time.

Littrell reportedly tried to press battery charges against Gallagher, but prosecutors decided not to after the video appeared to back up Gallagher's side of what happened.

In the affidavit, Littrell reportedly accused Gallagher of striking his hand and claiming Gallagher "was belligerent and disturbing the peace." But Gallagher reportedly told cops he was just "startled" by Littrell holding his phone so close to his face.

Ultimately, Walton County's Deputy Chief Assistant State Attorney Josh Mitchell reportedly cited "lack of criminal intent" as a reason he didn't recommend a warrant.

We've reached out to Brian's reps for comment ... so far, no word back.