Lindsay Lohan's girlfriend Samantha Ronson has slammed the actress' father Michael for claiming the DJ has been impersonating his daughter online.

Michael Lohan reacted angrily to a MySpace blog posted by the Mean Girls star last week which detailed her shock at finding out he had allegedly fathered a lovechild during his marriage to her mother.

Lindsay wrote, "I have gone through a lot in my past, and to be completely honest, I am still going through a lot right now. My father just let my family and I know that he had another child after my little sister Aliana, or maybe he had it before Aliana?? Either way, he cheated on my mother and that really sucks."

The elder Lohan fired back, admitting he believed there was a "99 per cent chance" the posting was actually written by Ronson.

But the DJ has laughed off the claim, insisting it was indeed written by the actress.

She tells New York gossip column PageSix.com, "Ha! That's funny, but I don't ghost-write MySpace blogs.

"Good thing he left that one per cent window open so he wasn't 100 per cent wrong for once."