A Roman Catholic priest serving several midcoast churches but who has worked throughout Maine is on temporary administrative leave while the diocese investigates a decades-old abuse allegation, officials said Monday.

According to the Roman Catholic Diocese of Portland, the Rev. Robert Vaillancourt has been accused of sexually abusing an underage girl in the 1980s. He has been placed on administrative leave while the diocese’s Office of Professional Responsibility conducts an internal investigation, consistent with the diocese’s protocol for such allegations.

Vaillancourt currently serves as pastor of St. Brendan the Navigator Parish, which is composed of Our Lady of Good Hope Church in Camden, St. Bernard Church in Rockland, St. Francis of Assisi Church in Belfast, and St. Mary of the Isles Churches on Islesboro, Vinalhaven and North Haven. He was also recently appointed as hospital chaplain of Maine Medical Center in Portland.

“Fr. Vaillancourt has denied any wrongdoing and indicated…