NHS England says the mental health trust that treated the killer who carried out the Nottingham attacks must attend monthly progress meetings to discuss improvements or face losing its licence.
Valdo Calocane received a hospital order after admitting the killings of Ian Coates, Grace O'Malley-Kumar and Barnaby Webber on 13 June 2023.
He was under Nottinghamshire Healthcare NHS Foundation Trust's care from May 2020 to September 2022.
NHS England's report details "a number of failings" found by a special review into the trust's services and outlines the steps it must take to improve, with a warning of "further formal action" if any of those steps are not met.