Kiribati and the Marshall Islands have detailed the human cost of nuclear testing in the Pacific, urging the United Nations to address the historic wrongs amid renewed calls for greater justice and accountability on the practice.

Speaking during global discussions on nuclear issues, Kiribati's ambassador and permanent representative to the UN said the pacific island nation continues to live with the consequences of nuclear testing which was carried out decades ago.

"Between 1957 and 1962, 33 nuclear tests were conducted in the South Pacific nation, yet the 500 citizens living on Kiritimati Island received little protection and inadequate warning," Teburoro Tito said in this week's New York session.

"The legacy of these tests has been devastating.

"Many of these people suffered untreatable illnesses and health complications, most of which resulted in death."

Mr Tito, the third president of Kiribati from 1994 until 2023, said the impact of the tests when the former British colony was called the Gilbert Islands continues to affect the tight-knit Micronesian community.

The worst of the cases included the contraction of a range of radiation-induced cancers in addition to severe abnormalities among newborn babies, he added.

The 72-year-old, who lived the nuclear testing era as a young child, said the continued suffering highlights the need for consequential justice and accountability by global powers, though there was no talk of financial or legal restitution.

"This profound human suffering underscores why (Kiribati) calls on all states' parties to address the importance of nuclear justice and recognise the role of affected communities," Mr Tito said.

"Kiribati's commitment to nuclear justice is also expressed through (its) remembrance and youth engagement, reflected in its support for artworks by young people from Kiritimati, envisioning a world free from nuclear weapons."

Kiritimati Island, known as Christmas Island during colonial times prior to independence in 1979, was at the centre of nuclear testing by the United Kingdom across the five-year period and the United States in 1962.

During the tests, the island's population was not evacuated, exposing both Kiritimati and Kiribati's residents to nuclear radiation.

Kiribati has been working closely with an unlikely ally to advance the issue further geopolitically, Mr Tito revealed.

"Together with Kazakhstan, we have been spearheading efforts on nuclear justice within this review cycle, the General Assembly (of the UN) and the Treaty on the Prohibition of nuclear weapons, including organising the first-ever international meeting on victim assistance and environmental remediation," he said.

The Marshall Islands added to the conversation, saying global nuclear risks are increasing despite past international efforts of worldwide disarmament.

"The world is slipping into a dangerous and growing level of nuclear risk," Marshall Islands ambassador and permanent representative to the UN, John M Silk, warned.

Mr Silk called for "building better bridges", while saying Pacific island states remain firmly committed to regional nuclear-free efforts under the Rarotonga Treaty.

The treaty's agreement establishes a nuclear-weapon-free zone in the South Pacific — which was signed in 1985 to prohibit the testing, stationing, acquisition, and use of nuclear explosive devices — as well as the dumping of radioactive waste at sea within their designated zone.

The Marshall Islands endured a total of 67 nuclear tests conducted by the US between 1946 and 1958 following Japanese occupation throughout much of World War II.

Mr Silk said the nuclear testing which targeted both the Bikini and Enewetak atolls of the Marshall Islands were of a "large scale" torment.

"Many of which were conducted after this country had petitioned the UN to halt them," he said.

"Despite assurances of our well-being, the tests continued under the auspices of the trusteeship resolutions."

The Marshall Islands UN delegate also spoke out to support Kiribati's initial proposal to address the impacts of nuclear testing.

Mr Silk backed the joint submission, underscoring the importance of progress on an outcome which recognises the "responsibility and obligation to address the historic wrongs and contemporary impacts of testing".

He also described the painful suffering experienced by Marshallese families following the nuclear tests.

Describing the experiences of Marshallese mothers who gave birth to stillborn babies which "looked like jellyfish", the 69-year-old lawyer recalled the voices of his country's past leaders who came to the UN halls in 1954 and again in 1956 to howls of protest which were largely ignored.

"As you walk these halls, if you take a few moments, you might hear their call to bring an end to nuclear weapons," Mr Silk said.