Photo © 2001 AFP Photo Lucy Nicholson

Gibson is embroiled in a bitter legal battle with his Russian ex-girlfriend, Oksana Grigorieva, over custody of their eight month old daughter, Lucia.

The couple split in April when their daughter was five months old.

Grigorieva apparently secretly recorded her conversations with Gibson, which were leaked to RadarOline over a week long period, but the gossip site has denied it got the tapes from her.

The tapes allegedly reveal Gibson threatening Grigorieva during a tirade of abuse.

Grigorieva has accused Gibson of physical abuse and one audio tape allegedly reveals an irate Gibson admitting it.

In one recording, Gibson allegedly demands sex from Grigorieva and calls her a "bitch on heat".

Gibson's soon to be ex-wife Robyn has reportedly signed a declaration in support of the actor, claiming Gibson never abused her or their children.

Meanwhile, Gibson could be facing possible criminal charges after LA County Sherriff detectives were granted access to court tapes for an investigation into domestic violence allegations against the actor.

It is not known if the tapes are the same as those posted online.