Tomihisa Taue, the mayor of Nagasaki, made the charge during a ceremony marking the 68th anniversary of the United States dropping an atomic bomb on his city, an event that led to Japan's surrender and the end of World War II, the Voice of America reported.
Twice during the memorial Taue said, "I call on the Japanese government to consider once again that Japan is the only country to have suffered a nuclear bombing," Kyodo News reported.
He charged Japanese Prime Minister Shinzo Abe was "betraying the expectations of global society" with his failure to sign a statement in April rejecting the use of nuclear weapons under any circumstances.
Taue said the prime minister's refusal "implies that the government would approve of their use under some circumstances."
Speaking at the same ceremony, Abe vowed Japan would make every effort to eradicate nuclear weapons.
At a similar commemoration Tuesday in Hiroshima, Abe told reporters "the severe reality" of North Korea had influenced his decision not to sign the statement.
Shohei Tsuiki, 86, who survived the Nagasaki bombing, alluded to the 2012 destruction of the Fukushima nuclear power plant when he said at the Friday ceremony, "It is obvious that nuclear power and human beings cannot coexist."