LONDON: Lindsay Lohan's lawyer has confirmed she is preparing a case against her client's father Michael, after a private phone-call between dad and daughter was leaked to the U.S. press.

The Mean Girls star recently threatened to file for a restraining order against her dad after he repeatedly pleaded with her to seek professional help for an alleged addiction to prescription drugs in a series of TV interviews and media events.

The actress branded her father a "lunatic", insisting he didn't "deserve" to have kids.

Despite the backlash from his daughter, Michael Lohan continued to tell reporters he had a collection of damaging taped chats with Lindsay and her mother Dina that he would release if she didn't try to kick her alleged habit.

Now, after a tape of a weeping Lohan breaking down to her father over the phone was obtained by TMZ.com, the star's lawyer is going after the actress' dad, stating she is currently trying to figure out if he broke the law by leaking the private conversation.

Lindsay's legal eagle Shawn Chapman Holley admits she is "exploring all options both civilly, and criminally," adding, "We are talking to legal authorities in New York and Los Angeles to determine if any laws were broken.

"This was a private phone conversation, and if this conversation took place in California then it was a violation of the law."

According to the site, Michael Lohan insists he has leaked the tape to prove to people his daughter is on the verge of a meltdown, but the actress/singer has taken aim at her father on social networking site - insisting the conversations are from years ago.

In a new post on her blog, she writes, "My father's such a loser & those recordings are from years ago. To release personal things is foul enough, but to edit them. I used to think that he needed the book for dummies on learning how to be a father.

"He's (sic) needs the book for dummies on How to be a man."