There's a new bombshell in the battle for ANNA NICOLE SMITH's newborn baby: Photojournalist LARRY BIRKHEAD has hired celebrity attorney DEBRA OPRI, who filed court papers on his behalf in L.A. Superior Court on Monday to establish paternity and custody of the child.

The allegations are stunning. Court papers reportedly claim that Anna Nicole was hospitalized to detox from a drug addiction.

That's just one of the jaw-dropping claims being made today. Sources tell ET that Anna Nicole has allegedly been addicted to methadone -- the same drug that was found in her son DANIEL's system when he died -- for nearly three years.

Birkhead also reportedly claims in the court papers that this pregnancy was not the first time Anna Nicole was pregnant with his child. Sources say the former lovers got pregnant, but that she miscarried in February of 2005.

Source