The 14-year-old from Lutterworth, Leicestershire, whose funeral took place yesterday, is said to have endured months of torment on controversial question-and-answer website Ask.fm before she was founded hanged in her bedroom two weeks ago.
Mr Cameron has said internet users should boycott “vile” websites which allow cyber-bullying to avoid more deaths of young people who receive abuse online.
He said website operators must “step up to the plate” to ensure users are protected.
Klavs Sinka, a co-founder of the Latvian-based website, told ITV News: “David Cameron was probably caught on the street in an interview like this, and commented without having the full information about the case.”
He added: “I’m not afraid to say that Ask.fm is one of the best controlled and moderated projects, you could learn from us.”
He said the affair showed the worst of the British tabloids, adding: “As a result, the information was distorted, that’s also why we’ve been avoiding any comments, because we see that we can say anything, but it will be twisted and turned back on us, regardless of what we meant.”
Ask.fm was criticised after Hannah’s death, and has since pledged to work with Leicestershire Police concerning the tragedy.
It has also engaged law firm Mishcon de Reya to carry out a full and independent audit of its site and safety features.
The website planned to announce yesterday the action it will take based on the lawyers’ recommendations, but said on Thursday night it would delay it until Monday as a mark of respect to Hannah.
Specsavers, Vodafone, Laura Ashley, EDF Energy and charity Save the Children all pulled adverts from Ask.fm in the aftermath of the schoolgirl’s death.