A lawyer says there are several legal obstacles to veterans of the Malayan Emergency claiming compensation for medical disorders suffered by their children.
Soldiers who served in the Malayan Emergency, a 12-year conflict following World War II, smeared the insecticide dibutylphthalate or DBP on the seams of their trousers and shirts to kill ticks and lice, which carried bush typhus.
World-first research published in the New Zealand Medical Journal has found that Malaya veterans' sons are up to eight times more likely than normal to get genital deformities and their daughters more than eight times more likely to get breast cancer.
Class action lawyer Grant Cameron says because the insecticide was used so long ago it may be difficult to find reliable witnesses and evidence.
He says the veterans would also have to prove conclusively the chemical is to blame for their children's conditions.
Mr Cameron says a better option might be to seek a government inquiry but warns it could take decades to win compensation.
Thousands of soldiers used chemical dozens of times
The man who first suspected a link between the insecticide used by New Zealand soldiers and medical disorders in their children says thousands of men used the chemical dozens of times.
Jack Stanaway was the first person to suspect a link, when the name of the insecticide came up during research he was doing on his son's condition.
He approached the Malaya Veterans Association and eventually Canterbury University, which did the study. Mr Stanaway told Checkpoint he now feels angry that his suspicions have been confirmed.
"At the time," he says, "we were not told that there was any risk with the continued use of it."
Veterans long suspected a link
A professor of toxicology at Canterbury University, Ian Shaw, says the study is the first in the world to show an association between fathers' exposure to DBP and health problems in their children.
However, he says while the study shows a link, and the odds are that the insecticide is the cause, that has not been proved.
Malaya Veterans Association national secretary Hiro Hamilton says veterans have always known there was a link, and they have been pushing for several years for research to be done.
He says he is not sure how the Government will respond to the research but the association is likely to seek compensation.
The 71 veterans in the study had 155 children between them.