The use of restraints on children and adolescents in mental health wards at two Newcastle hospitals has risen, the Care Quality Commission (CQC) found.
It follows inspections at the Ferndene inpatient centre in Prudhoe and the Alnwood unit at St Nicholas Hospital.
Assessors found a "significant increase in restrictive practices" since 2018.
Cumbria, Northumberland, Tyne and Wear NHS Foundation Trust said it was "building on its ongoing work to reduce restrictive interventions".
The November inspections followed concerns raised by a whistleblower about staffing, patient safety and the quality of care and treatment.
Wards were found to be sufficiently staffed by professionals who managed risks to patient safety effectively.
Young people told inspectors they felt safe and staff supported them.
However, instances of restrictive practices - including the use of belts and cuffs - were found to have increased significantly since a previous inspection in 2018.
The report said: "There was little evidence to show what interventions had been put in place to challenge the high levels of restrictive practice being used, including mechanical restraint, or that the least restrictive approaches were being considered for those patients that were subject to the use of restraint, including mechanical restraint."
It said the trust should "review the use of restraint and mechanical restraint", which should be used as a "last resort", and called for a "clear debrief process" when restraints were used.
John Lawlor, the trust's chief executive, said: "We are committed to reducing levels of restraint.
"Work is under way to ensure that the required improvements to debrief processes are implemented, and we have already seen an improvement.
"We will continue to build on the ongoing work to reduce restrictive interventions, in particular our Talk 1st programme, a trust-wide initiative which aims to decrease restraint and aggression on our wards."