SYDNEY, Australia — In the lead-up to a vote on legalizing same-sex marriage in Australia, vitriolic campaign materials, including fliers calling homosexuality “a tragedy of a family,” circulated this week in Melbourne and Sydney.

The fliers, the latest salvo in a heated national debate that has involved politicians and religious leaders, were denounced by Prime Minister Malcolm Turnbull on Tuesday.

People will “often say things that are hurtful and unfair and sometimes cruel, but that is part of a debate,” Mr. Turnbull said after same-sex marriage activists called on him to condemn what they described as “vilification.”

“I deplore disrespectful, abusive language whether it is directed at young gay people, or other religions or other races,” he said.