The inspection and regulation body has criticised the privately run children’s home, saying it has identified “serious and widespread concerns”.
The home is not named in the report published by Ofsted but is run by Cambian Childcare Limited.
The company said it is taking steps to address the concerns raised and expected to “swiftly” return to a standard it expected of its homes.
The children’s home can provide care for up to three children who experience social and emotional difficulties.
However, at the time of the most recent inspection, only one child was living at the home.
The last full inspection of the children’s home was in April this year.
Ofsted rated the home as “requires improvement”, at the time saying the children’s home was “not yet delivering good help and care for children and young people”.
Ofsted said the assurance inspection which took place in July was brought forward because of “concerning notifications and information received” about the child’s safety.
In a report published by Ofsted inspectors said the child was at “significant risk of harm”, highlighting that staff had failed to respond to all safeguarding incidents in a way that protected the child’s safety.
The report said: “On one occasion there was a significant delay in staff searching for the child when they had reported the child missing from home.
“This is despite known information that suggested the child was at risk of harm.
“On another occasion, staff did not explore all opportunities to encourage the child to return home, in accordance with the home’s model of support.
“Staff identified concerns during a search of the child’s room. They demonstrated a lack of professional curiosity to understand the associated effects and risk of the child in relation to unknown substances found.
“In another instance, staff did not take the child to hospital when they were advised to do this by a health professional or seek alternative medical support when the child refused to go.
“This does not provide the necessary assurances that staff are doing all that they can to ensure the child’s welfare.”
Ofsted did highlight that staff supported “positive experiences” for the child, adding that interests and hobbies were encouraged, with the child attending a weekly boxing class.
The report also said that leaders had recently advocated for the child and “appropriate and constructive challenges” had been made to other professionals when responses were “insufficient”.
Inspectors added that a social care manager had also given positive feedback after recent discussions with managers about supporting the well-being of the child.
A spokesperson for Cambian Childcare Limited said: “We have and are taking steps to address the concerns raised by Ofsted, with a new manager in the home and with focused support we expect the home to swiftly return to a standard we expect.”