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A new report about New Zealand seamen irradiated during hydrogen bomb tests in the Pacific could help the sailors' class action suit against the British government, their lawyer says.

Five hundred and fifty-one Kiwi sailors on board the frigates HMNZS Pukaki and HMNZS Rotoiti were at the series of nine aerial bomb explosions at Christmas Island in the Pacific and Malden Island, part of Kiribati, beginning on May 15 1957.

Massey University researchers released a study yesterday which said the sailors' attendance at the tests caused genetic damage and high counts of rare chromosomal abnormalities.

The lawyer representing the New Zealand sailors, Gordon Paine, said today the study articulated what the sailors had long felt and believed -- that being at the tests had caused them permanent damage.

"Whether the report will impact on the case will be up to the experts," he told NZPA.

The sailors, banded together as the New Zealand Nuclear Test Veterans Association, were part of the class action suit lodged last year against the British Ministry of Defence.

Mr Paine would go to Britain next month to take the next steps in the suit, which was before the courts.

The New Zealanders had joined with other former members of the British and Fijian armed forces who had been at the tests, he said.

How many people were taking part in the class action, from New Zealand and in total, had yet to be finalised.

"There is still a lot of work to be done to work out who meets the criteria to be part of the action. Our view is every New Zealand seaman who was involved in Operation Grapple should be represented," Mr Paine said.

The sailors have long claimed being irradiated at the test sites affected them and their children.

Now, the study has found cellular abnormalities in the veterans and blames radiation exposure.

The study, led by Dr Al Rowland, tested 50 seamen involved in the tests, compared to 50 control subjects.

Dr Rowland's previous research has included a study of the effects of the defoliant Agent Orange on New Zealand soldiers during the Vietnam War. He had also done other studies into the health of veterans of Operation Grapple.

He said the results of his latest study were indicative of the veterans having incurred "long term genetic damage as a consequence of performing their duties relating to Operation Grapple".

Prime Minister Helen Clark yesterday told reporters the research was of "great interest" and the Government would study it further.

The Government had contributed financially to this research "because we'd all like to know the truth about what happened".

"By today's standards obviously it's simply extraordinary that people were ordered to stand on the deck of a frigate and witness an atmospheric test."

It would be hard to believe veterans suffered no health effects as a result of watching the nuclear tests.

"The question is what damage... Was it a health effect at the time, or did it do the sort of damage that this study appears to be pointing towards?"

Green MP Sue Kedgley said the Government must acknowledge the suffering, adverse health effects and long term genetic damage the veterans had incurred.

"They deserve an official apology from the Government and compensation for the suffering they have endured," she said.

"The Government must also agree to their request that their children are tested as well, to see if genetic damage has been passed on."

National MP Judith Collins said the research provided significant new information.

It was time the Government listened to the concerns of nuclear veterans, she said.

"The Government must now carefully consider the report and take advice on what the next steps should be."

That is what Miss Clark and Veterans Affairs Minister Rick Barker said they would do.

"We now need to consider the research and in the interim we encourage any nuclear test veteran who has a disability that they believe is attributable to or aggravated by their service to apply for a War Disablement Pension," Miss Clark said.

Mr Barker said that if a pension was awarded then all medical care for that disability would be fully funded.

New Zealand Nuclear Test Veterans Association chairman Roy Sefton yesterday said many of the veterans exposed to the nuclear blasts have had shorter life spans and chronic bad health, and in many cases, so had their children.

He was on board HMNZS Pukaki during the tests.

During the explosions, sailors on deck watched -- wearing only denim coveralls, masks and gloves. Clean-up crews wore thicker nylon suits, carried Geiger counters and washed down irradiated parts of the ships' superstructures. Other crew members were in special shelters in the bowels of the ships.

But it probably wasn't so much the blasts that exposed the sailors as the weather monitoring when seamen wearing shorts and scandals spent their days on the deck, washing in and drinking rainwater, Mr Sefton said.

"That's probably where we were exposed to most of the fallout -- in the rain," he said.