The Group of Seven industrialized nations should declare a nuclear weapon "no first use" policy during a summit in May in Hiroshima, the former mayor of the atomic-bombed Japanese city said in a speech on Saturday in London.

Japan, as host of the summit, can lead efforts to pressure Russian President Vladimir Putin to not use nuclear weapons in his war on Ukraine, but G-7 members should "aim higher," said Tadatoshi Akiba during a ceremony where he received a peace award from a British Islamic group.

Former Hiroshima Mayor Tadatoshi Akiba delivers a speech after receiving a peace award from a British Islamic group in London on March 4, 2023. (Kyodo)

"The G-7 Hiroshima declaration should be the starting point for the universal 'no first use' of nuclear weapons," the 80-year-old added.

Japanese Prime Minister Fumio Kishida, a lawmaker representing a constituency in Hiroshima, has vowed to pitch his vision of a world without nuclear weapons at the summit, which will be joined by leaders from other G-7 members -- Britain, Canada, France, Germany, Italy and the United States, plus the European Union.

However, Japan remains in a policy dilemma when it calls for the abolition of nuclear weapons while at the same time relying on U.S. weapons for protection.

Akiba, who served as Hiroshima mayor for 12 years through 2011, slammed as "a fantasy" the belief that "the possession of and threat of use of nuclear weapons guarantee that no nuclear powers will use such weapons."

Holding up a graphic photo of a young victim in Nagasaki, the second Japanese city to suffer a U.S. atomic bombing in 1945, Akiba said the boy was "thrown into a living hell."

"We should not let this happen again anywhere, anytime, to anyone," he emphasized, saying scenes like this photo come to the minds of atomic bomb survivors when Russia rattles its nuclear saber.

Akiba expressed hope the G-7 will unite on "no first use," saying that the leaders of the countries, as part of the Group of 20, have already signed a declaration in Indonesia in November that affirmed "the use or threat of use of nuclear weapons is inadmissible."

The United States considered adopting a "no first use" policy when Barack Obama, who pledged in 2009 to pursue a world free of nuclear weapons, was president. But his administration gave up the idea in the face of objections from some allies including Japan.

The U.S. administration of President Joe Biden also rejected declaring "no first use" in its Nuclear Posture Review released last year, while saying it would only consider using nuclear weapons in "extreme circumstances" to defend itself and its allies.

Akiba received the award from the Ahmadiyya Muslim Community, in which past recipients included Canada-based atomic bomb survivor Setsuko Thurlow, according to the group.