Shiro Suzuki made the remark after the Group of Seven industrial powers adopted a separate document on nuclear disarmament in May that called for using nuclear weapons as deterrence.
"Now is the time to show courage and make the decision to break free from dependence on nuclear deterrence," Suzuki said in his peace declaration on Wednesday.
"As long as states are dependent on nuclear deterrence, we cannot realise a world without nuclear weapons."
Russia's nuclear threat has encouraged other nuclear states to accelerate their dependence on nuclear weapons or enhance capabilities, further increasing the risk of nuclear war, and Russia is not the only one representing the risk of nuclear deterrence, Suzuki said.
The US dropped the world's first atomic bomb on Hiroshima on August 6, 1945, destroying the city and killing 140,000 people.
A second attack three days later on Nagasaki killed 70,000 more people.
Japan surrendered on August 15, ending World War II and its almost half-century of aggression in Asia.
At 11.02am, the moment the bomb exploded above the southern Japanese city, participants at the ceremony observed a moment of silence with the sound of a peace bell.
Suzuki expressed concern about the tragedy being forgotten as time passed and memories fade.
Survivors have expressed frustration about the slow progress of disarmament, while the reality of the atomic bombing and their ordeals are not yet widely shared around the world.
The concern comes after widespread reaction to social media posts about the "Barbenheimer" summer blitz of the Barbie and Oppenhheimer movies that triggered outrage in Japan.
The combination of Barbie and a biography of J Robert Oppenheimer - who helped develop the atomic bomb - sparked memes including mushroom clouds.
The craze was seen as minimising the ghastly toll of the Nagasaki and Hiroshima bombings.
Suzuki, whose parents were hibakusha, or survivors of the Nagasaki attack, said knowing the reality of the atomic bombings was the starting point for achieving a world without nuclear weapons.
He said the survivors' testimonies were a true deterrence against nuclear weapons use.
Prime Minister Fumio Kishida, who did not attend the memorial in person, acknowledged in his video message that the path toward a nuclear-free world has grown tougher because of rising tensions and conflicts, including Russia's war on Ukraine.
Also weighing on the disarmament movement is a deeper division in the international community.
Kishida, who represents Hiroshima in parliament, has sought to showcase the G7 commitment to nuclear disarmament but has angered the survivors for justifying nuclear arms possession for deterrence and for refusing to sign the Treaty on the Prohibition of Nuclear Weapons.
Suzuki demanded Kishida's government and national MPs quickly sign and ratify the treaty and attend the upcoming meeting as an observer "to clearly show Japan's resolve to abolish nuclear weapons".
As Washington's ally, Japan is under the US nuclear umbrella and seeks stronger protection as the allies reinforce security co-operation to deal with threats from China and North Korea's nuclear and missile advancement.
Under its new national security strategy, Kishida's government is pushing for a military build-up focusing on strike capability.
As of March, 113,649 survivors, whose average age is 85, are certified as hibakusha and eligible for government medical support, according to the Health and Welfare Ministry.
Many others, including those known as victims of the "black rain" that fell outside the initially designated areas, are still without support.
