Chatbot versions of the teenagers Molly Russell and Brianna Ghey have been found on Character.ai - a platform which allows users to create digital versions of people.
Molly Russell took her life at the age of 14 after viewing suicide material online while Brianna Ghey, 16, was murdered by two teenagers in 2023.
The foundation set up in Molly Russell's memory said it was "sickening" and an "utterly reprehensible failure of moderation."
The platform is already being sued in the US by the mother of a 14-year-old boy who she says took his own life after becoming obsessed with an Character.ai chatbot.
In a statement to the Telegraph, which first reported the story, external , the firm said it "takes safety on our platform seriously and moderates Characters proactively and in response to user reports."
Andy Burrows, chief executive of the Molly Rose Foundation, said the creation of the bots was a "sickening action that will cause further heartache to everyone who knew and loved Molly".