Devastated Chris Bell’s 17-year-old daughter Megan died at the festival staged at Strathallan Castle last month.
Mr Bell, 44, said his family had been “left in the dark” over his daughter’s death and is demanding a full inquiry.
He has set up an online petition asking for the age limit to be raised at music festivals to 21.
He said: “The stories that we heard since mainly include youths taking drugs and drinking heavily. I strongly believe that an adult would not experiment or adhere to peer pressure like a child would.”
Mr Bell said drugs were not part of Megan’s life and believes her drink may have been spiked.
Organisers of Scotland’s largest outdoor music festival were facing growing pressure after pathologists confirmed that three deaths linked to the event were drug-related.
Drugs have been blamed for the death of 29-year-old father-of-three Jim Richardson, whose body was found in a field two days after the event in Perthshire in July.
A verdict of “presumed drugs related” has also been recorded for teenagers Megan and Peter McCallum, also 17, who both died in a temporary hospital on the site of the festival.
Conservative MSP for Mid Scotland and Fife, Murdo Fraser, said: “Festival organisers must take responsibility for public safety, and that includes discouraging the use of narcotics.
“An approach where drug use is seen as part and parcel of the festival cannot be allowed to continue - lessons must be learned.”
The circumstances around Jim Richardson’s death and Police Scotland’s initial response are under investigation by a force watchdog.
The verdicts have sparked fresh calls for festival organisers DF Concerts to show they are cracking down on drug abuse ahead of next year’s event.
Liz Smith, also a Conservative MSP for Mid Scotland and Fife, has demanded “renewed efforts” from police and organisers to educate revelers about the dangers of illicit substances. She has also suggested more drug-detection dogs at the festival site.
Mr Richardson was on the bus home on Monday, 11 July, when it stopped on the A9, near Auchterader.
He got off for a cigarette at around 2.30pm, but never returned. Mr Richardson texted his wife Samantha in Wishaw to say he had been left at the roadside without his belongings.
He was found dead several miles away at Wester Cairnie Farm, near Forteviot, the following morning.
His death initially baffled police, who said he appeared to have no noticeable injuries.
Now an autopsy has concluded that the railway track engineer’s death is “presumed drug related”.
Mr Richardson’s death certificate notes that further laboratory investigations are pending.
Pathologists have ruled that he died at 9.50am on July 12 in a field adjacent to the A9.
Mr Richardson was the third death linked with this year’s T in the Park festival.
Megan, from Seaham, County Durham, died in the early hours of 8 July after collapsing in the festival’s Slam dance tent on the first night of T in the Park
The teenager’s cause of death has been recorded as “no anatomical cause identified, presumed drugs related (laboratory investigations pending)”.
The same cause was noted for student Peter MacCallum who died at 6.30am the same day.
Both teenagers, whose deaths are said to be unconnected, died at the temporary hospital facility at the Strathallan Castle site.