Kayti Edwards, who has urged police to widen their probe into the 54-year-old actor's death last October, said he once told her chillingly: "I'm in with the doctors."
Five people, including Matthew's live-in personal assistant and two medics, have been charged over his death at his Los Angeles home.
California Attorney Martin Estrada said the doctors "took advantage of Mr Perry's addiction issues to enrich themselves" by supplying him with a large amount of ketamine.
Jasveen Sangha, 41, who, according to prosecutors, was known as "the Ketamine Queen", Salvador Plasencia, known as "Dr P", and Erik Fleming, an acquaintance of Perry, are among those charged.
But Kayti, 47, said: "There's a whole network of people beyond those facing criminal charges who the police need to investigate.
"Detectives need only delve back into [Matthew's] medical history.
There are so many more doctors who have been on his books over the years who will be terrified right now.
"Whenever he was in active addition, he knew instantly where to turn. It's a scandal." Kayti, the stepgranddaughter of veteran British actress Julie Andrews, 88, dated Matthew in 2006 before becoming his assistant in 2011. They remained friends until his death.
She said: "Ketamine was his new thing, but it all started with unscrupulous doctors over-subscribing prescription pills like Vicodin.
"When the charges dropped, I knew they would be doctors.. because that was what he always did.
"His addictive brain would think 'Well, it was prescribed from a doctor so I can take it'. In his head, it wasn't like he was out on the street scoring drugs."
When she worked for him, Kayti was shocked by the sheer quantity of drugs Perry, who played Chandler Bing in the blockbuster US TV series, was consuming.
Denne historien er fra August 24, 2024-utgaven av Daily Express.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent ? Logg på
Denne historien er fra August 24, 2024-utgaven av Daily Express.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent? Logg på
THE ART OF WAR
Boss lauds 'ugly' derby win after sleepless nights blight build-up
CLOCK-WISE
Newcastle wake up in time to stun dominant Wolves
Vu's late burst ends brave European rally
LILIA GETS AMERICANS OVER LINE
'Miracle' Triple Layer Insoles stopped my husband's knee and foot paint!
They also turned him from a grumpy old grouch to being active, pain-free and happy again! And got my life back too!
Why teens are hooked on Friends 20 years on
The one where a new generation of fans is devoted to the hit TV show three decades after it first aired... Debbi Marco takes her children to an immersive experience bringing the iconic TV sitcom back to life
FINAL JOURNEY OF THE UNKNOWN WARRIOR
In the final extract from his impossibly moving new book, RAF veteran John Nichol reveals how the remains of ONE anonymous fallen serviceman were chosen to represent ALL of Britain's First World War missing
Space billionaire returns to Earth with a splash
THE first non-astronaut to walk in space landed back on Earth yesterday after an epic five-day trip.
'I feel I'm having one of the greatest decades of my life'
DAVINA McCall is relishing fulfilling lifelong her 50s career ambitions, scooping an MBE and finding happiness with partner Michael Douglas.
Putin hands Iran nuclear secrets in return for ballistic missiles
FEARS were growing in the West last night that Russia gave Iran nuclear secrets in return for ballistic missiles to use in its bombardment of Ukraine.
William wishes Harry a happy 40th birthday
KATE and William sent greetings to Prince Harry on his 40th birthday yesterday as they followed the lead of the King.