MONTPELIER — The number of mentally ill Vermonters being held in hospital emergency rooms for lack of a mental health bed is ‘‘heading in the wrong direction,’’ the state’s top mental health official told lawmakers Tuesday.

Mental Health Commissioner Patrick Flood told the Legislature’s Joint Mental Health Oversight Committee that ­instances in which mental health beds were not available and patients were held in hospital emergency rooms grew from 15 in June to 22 in July and 24 in August.