Olivia McTaggart released her findings in Launceston on Wednesday.

She said the girl, 11 months old, who cannot be identified for legal reasons, died in the early hours of January 27, 2013.

Ms McTaggart said the baby died either before, during or after her parents engaged in some form of sexual activity on the bed.

However, she said her death more likely occurred when the baby was trapped under the bedding, by or in proximity to the adults' bodies.

Ms McTaggart said the bed included cushions underneath the mattress.

"The sleeping environment is dangerous for such an infant," she said.

The coroner made critical findings against both parents and child protection services.

Ms McTaggart said the parents had her sympathy, but it was they who had created this unsafe situation which ended up with their daughter's death.

"I intend to refer the evidence from the inquest to the Director of Public Prosecutions for consideration," she said.

Both parents were in court when the findings were handed down.