Michael Lohan claims Lindsay has found it easy to obtain prescription drugs, which he claims she is addicted to, because medical professionals prescribe them too freely.
He said in an interview on Australia's Kyle and Jackie O radio show: "It's horrible. When a child is growing if they have some kind of a psychological or medical problem it is diagnosed and you get something like Ritalin or Prozac, then they diagnose it at that age. That is medical fact. You don't all of a sudden develop it at 18.
"Doctors and the internet have to be held accountable. The people selling these drugs. they're so readily available it's insane. Once they get in your system, they're harder to detox from than illegal drugs."
Michael says he will not stop until he has helped the 23-year-old actress "get her life back".
Lindsay appeared in court last week in relation to her 2007 driving under the influence (DUI) charge, and Michael is unhappy about the way she was treated.
Her probation was extended by a year to give her time to complete alcohol education classes, but Michael thinks she should have been sent to rehab.
He said: "I want to go out and speak to the judge who let Lindsay walk out of the courtroom without any kind of a drug test or anything. Seeing the condition she was in when she walked into the court. if you're on probation and you did that you'd be in jail. A better resort would be rehab, Lindsay needs a rehab to get off the prescription drugs."
Michael added he is seriously considering applying for a conservatorship order - which would see him placed in charge of Lindsay's personal and professional affairs - if things do not change.
He said: "There's different ways of seeking conservatorship - if someone's threatening themselves, or might harm themselves, or can't make decisions for themselves. If it gets to that point I'll have to prove the reasons I need it and then we'll all know."