Lindsay Lohan's father refuses to believe she has stopped taking prescription drugs.

Michael Lohan - who has repeatedly insisted his daughter is addicted to legal medications - dismissed claims the troubled actress has quit some of the medically prescribed pills she takes for various conditions ahead of her 90-day jail term, which starts next week.

Michael - who is estranged from his family - said: "If it's true, I couldn't be happier. But I have No Doubt that this is just another lie, spewing from her mother Dina's mouth."

Lindsay currently takes five prescription medications - Nexium for heartburn, antidepressants Zoloft and Trazodone, Adderall for Attention Deficit Disorder (ADD) and painkiller Dilaudid for "dental pain" - and Michael is sceptical she has been able to stop taking some of them because they require a long weaning process.

He added in an interview with RadarOnline.com: "You can't just stop taking those medications. You have to be weaned off with a doctor's supervision. The amount of meds she's been on and the amount of time she's been on them. she would definitely need medical supervision. So no, I don't think she has stopped."

In April, Michael attempted to stage an intervention to save Lindsay from her substance abuse, and in May he wrote a letter to a judge asking for her to be ordered to rehab in relation to her DUI charge.

Meanwhile, Lindsay has blasted her father in a rant against comedienne Joan Rivers, who recently posted a series of messages online mocking the actress over her legal difficulties.

Lindsay tweeted: "Joan Rivers and her "stargument" make me believe that she and Michael Lohan are a match made in heaven...all he needs is her botox doctor. "Dr." Drew- any ideas? Botox rehab reality show?

"in the words of 50 Cent.. "You shouldn't throw stones if you live in a glass house and if you got a glass jaw, you should watch yo mouth. (sic)"