The parents of a woman who killed herself after being discharged from a mental health unit are petitioning for a patient confidentiality law change.
Sarah Moore, 27, left the Radbourne Unit, in Derby, on 19 February. Her body was found in a park the next day.
Robert and Diane Moore believe their daughter would still be alive had they been told she had left the unit.
Derbyshire Healthcare NHS Foundation Trust said it had "a duty to respect" patients' wishes.
The trust added that it was investigating Ms Moore's death and would implement any changes identified.
Mr and Mrs Moore have set up the petition calling for patients sectioned under the Mental Health Act not to have the right to patient confidentiality, if it affects their safety.
According to Ms Moore's medical records, she had told hospital staff on several occasions she wanted to end her life.
Mr Moore said his daughter was in "no fit state of mind to make decisions".
"There should be a change in the law where you should have the right to know what is happening to your loved one while they are sectioned in a psychiatric unit.
"It is absolutely horrendous," he said.
Mrs Moore added: "If I had known when she had left, she probably would have answered me and it all would have been avoided."
The couple said their daughter's death had "destroyed" them.
The trust said it had "a duty to respect the wishes of those who use our services, including discussions around their discharge from hospital.
"Maintaining people's confidentiality is very important and enshrined in law."