Former Vice President Nguyen Thi Binh said there were an estimated three million people affected by Agent Orange used by US forces during the war.
Hundreds of thousands have died, while others remain sick and are living in poverty, she said.
"We are expecting the US government and the companies which produced Agent Orange to realise their spiritual, moral and also legal responsibility," she said.
About 40 Agent Orange victims attended the event, including veterans and children. Some had deformed legs, others had dark patches covering their faces and some were mentally disabled.
The Vietnam Association for Victims of Agent Orange hopes to attract humanitarian support and donations from within Vietnam and overseas.
"We have been waiting for this association for a long time. I hope it will do more to help the victims"
Bui Dinh Hy,
Agent Orange victim
"We have been waiting for this association for a long time," said Bui Dinh Hy, a veteran who was exposed to Agent Orange and has tumours covering his face and body, and whose children were also born with deformities. "I hope the association will do more to help the victims."
In 2000, Prime Minister Phan Van Khai approved a plan to provide monthly stipends ranging from 48,000 dong (US$3) to 100,000 dong (US$6.40) to government workers, soldiers and civilian volunteers who fought for the Communists in heavily sprayed areas during the war.
Their disabled children were also included in the plan.
Those affected by Agent Orange who fought for the US-backed South Vietnamese government were excluded from the allocation.
Binh said assistance from the government, Vietnamese people, foreign governments and non-governmental organisations is still small compared to victims' needs, especially since Agent Orange has now affected three generations in some provinces.
"Overcoming the consequences of Agent Orange is more difficult and takes longer than we anticipated," Binh said. "We therefore need to have more active and efficient measures."
"We are expecting the US government and the companies which produced Agent Orange to realise their spiritual, moral and also legal responsibility"
Nguyen Thi Binh,
Former Vietnam Vice President
An estimated 72 million litres of defoliant, primarily Agent Orange, were sprayed by US planes in Vietnam between 1962 and 1971 to destroy forest cover that might shield Communist troops during the war.
The defoliant contained dioxin, a highly toxic substance, and has been linked to a variety of illnesses, including cancer, diabetes and spina bifida.
In 2002, Vietnam and the United States held their first joint scientific conference on Agent Orange and its effects since the war ended in 1975.