Wellington  - Leaders of all eight political parties in the New Zealand parliament joined on Wednesday in making a formal apology to veterans who fought in the Vietnam War 40 years ago for their treatment.

Speaking on behalf of the Crown, Prime Minister Helen Clark apologized to the 3,400 troops who served in Vietnam between 1964 and 1972 for sending them into a toxic environment where the dioxin herbicide Agent Orange was widely sprayed and then ignoring illnesses they and their children suffered as a result.

The Vietnam veterans have long harboured deep resentment over their treatment after taking part in New Zealand's longest and most controversial military engagement of the last century.

Unlike those who came back from two world wars, they were given no heroes' welcome home parades but were flown back in the dead of night and told not to wear their uniforms in the streets or tell people where they had been. Some were called "baby-killers" and spat on.

Acknowledging their dedicated service, Clark said, "Those armed forces personnel loyally served at the direction of the New Zealand government of the day, having left their home shores against a background of unprecedented division and controversy over whether or not New Zealand should participate in the war.

"The Crown extends to New Zealand Vietnam veterans and their families an apology for the manner in which their loyal service in the name of New Zealand was not recognised as it should have been, when it should have been, and for inadequate support extended to them and their families after their return home from the conflict."

Clark, whose own Labour Party opposed the war and ordered the troops withdrawn when it came to power in 1972, said it was a defining event in New Zealand's recent history, during which "significant divisions and tensions emerged within our own society."

"We honour the 37 personnel who died on active duty, the 187 who were wounded, some very seriously, and all those who have suffered long-term effects," she said.

"The service of those who fell and all who served in that conflict should now be honoured, alongside that of other brave service personnel deployed to other conflicts in the service of our country."

Clark said successive governments had ignored the veterans' concerns about the health effects of Agent Orange, which US forces sprayed to defoliate the jungle and deny cover to Viet Cong guerrillas, for too long.

She noted that Vietnam had suffered huge damage to its people, cities, ports and countryside during the war with long term and inter-generational consequences.

John Key, leader of the opposition conservative National Party, which originally committed forces to support the US war in Vietnam in 1964, also apologized, saying, "The New Zealanders who were asked to serve in this war were not responsible for the decisions taken by politicians at the time, and they should not have been treated as though they were.

"New Zealand has not treated these veterans well," he said. "The service they carried out in the name of this country has often gone unacknowledged or been conveniently forgotten.

"The treatment they received, both in Vietnam and then in the years after their return to New Zealand, was unfair and unacceptable."

Tariana Turia, co-leader of the Maori Party, supported the apology on behalf of the indigenous Maori minority, who she said accounted for 65 per cent of New Zealand troops sent to the war, and called on the government to apologize also to the people of Vietnam.

The government's apology was part of a reconciliation package negotiated with veterans' representatives in 2006 which will include the first official welcome home parade they have been awarded, in Wellington this weekend, nearly 36 years after the last troops returned. (dpa)