Molly Russell’s father says legislation to prevent minors from viewing hazardous content should be passed immediately.
An investigation concluded that social media posts “more than minimally” led to Molly’s suicide in 2017 after she committed a self-harming act while depressed.
The coroner ruled she saw images that “shouldn’t have been available” to her.
Ian Russell said: “It’s clear to me that the age of self-regulation on internet platforms must be ended for the sake and safety of our children.”
He told BBC Radio 4’s Today programme: “The current government has said that they want the UK to be the safest place in the world to be online and yet we’re still here and we’re not regulating the platforms.
“I think it’s really important, firstly, that something that is illegal in the offline world must be illegal and we must be better protected when it’s found on the online world.
“And I think the hardest thing that the online safety bill is tackling is perhaps this content that’s described as ‘legal but harmful.”
Andrew Walker, the senior coroner for north London, said Molly, from Harrow, north London, appeared a healthy girl who was flourishing at school, having settled well into secondary school life and displayed an enthusiastic interest in the performing arts.
However, Molly had become depressed, something common in children of this age, the coroner said. The inquest was told her condition worsened into a depressive illness.
Mr Russell also described the impact the inquest has had on his family.
He said: “When the verdict came in, I think we were quite numb and we’re still processing it.
“It was exhausting for us as a family. It was two weeks in court, but five years since Molly died.
“It’s just extraordinary, overwhelming grief that I think probably is one of the strongest emotions that anyone can ever feel.
“So, the inquest itself couldn’t compete with those early days of huge grief and just struggling to get by a second sometimes.
“But it really did reconnect us we miss Molly and how much we wish she hadn’t seen that content and that she was still with us.”