Britney SLAMS Ex-Hubby -- 'Kiss My Lily White Ass'

Britney Spears just lashed out against her ex-husband Jason Alexander -- and both of the publications responsible for publishing a phone call allegedly featuring her voice -- advising them all to "Kiss my lily white southern Louisiana ass!"

As we previously reported, Britney claims the person on the tape is not her -- and her lawyer has already threatened legal action against everyone involved in its release. 

Audio Expert: Britney Recording Was 'Manipulated'

A highly-respected audio expert tells ... Jason Alexander's recording of the woman he claims is Britney Spears "has been electronically stepped on."

Tom Owen of OWL Investigations, and Chairman of the Audio Engineering Society Standards Committee of Forensic Audio,  the tape was "doctored" to such a severe extent, there's no way to conduct a meaningful voice-recognition test.

Owen says the tape has been "stepped on at least 3 times." With noise reduction, equalization and removal of voice qualities such as natural timbre, sibilance and tonal qualities, it's impossible to determine whether Britney's voice is on the tape.

Owen says Britney has a "very vanilla voice" and that with manipulation it wouldn't be that difficult to make someone sound like her.

Britney Pays Visit to Jason Trawick At Work

Britney Spears went to the William Morris Endeavor Entertainment agency in Bev Hills this afternoon ... to visit boyfriend Jason Trawick in a show of solidarity.

Britney spent time with Jason inside the building, left by car and then returned.  The pic of Brit (above) is her coming back to the agency to see her BF.

We also got this pic of Jason outside William Morris, where he works as an agent. It's interesting, because Jason's not running for cover.  

Our sources say Trawick has been adamant today ... the voice on the recording is not his girlfriend's.  Jason joins Britney's camp in slamming the publication of Jason Alexander's audio tapes, in which he claims Britney told him Trawick beat her.