Heath Ledger's father has revealed the conversation the movie star had with his sister the night before he died.

The Oscar-winning Perth actor was found dead in a New York apartment from a prescription drug overdose 10 years ago.

Speaking on Nova's Addicted podcast, Mr Ledger said his daughter Kate had warned her brother not to mix medications.

“Heath's sister was literally talking to him the night before saying 'You can't mix the opioid medication you are taking for your chest infection with sleeping tablets’”, he told host Ash Bradnam.

Heath Ledger's father Kim and sister Kate Ledger hold the Oscar for best supporting actor on behalf of Heath Ledger. Picture: AP

"Ever since he was young he was always very wired and busy. He was meeting someone the next morning and he said ‘Kate, I'm going to take a couple of sleeping tablets’

“She warned him, she said ‘You can't mix these substances’”.

Mr Ledger is a patron of Scriptwise, an organisation which is lobbying for a national real-time monitoring system to crack down on “doctor shopping” by people hooked on prescription drugs.

The fear of addiction was so great for Mr Ledger after his son's death that he refused to take a certain pain killer after a knee operation.

Heath Ledger was found dead in a New York apartment in 2008.

“I remember during the autopsy … there was an element of that (oxycodone) in there,” he told the podcast.

“They said ‘that mixed with this can be quite dangerous’”

When asked about his initial reaction to Heath's fatal overdose, Mr Ledger revealed he first learnt of it he turned on the TV and saw a news report.

"We literally turned on the television on [and] the first thing I saw was them carting the stretcher out. That's the vision that will always stay with me. I couldn't believe it."