David Lange, former prime minister of New Zealand

WELLINGTON, New Zealand -- Former New Zealand prime minister David Lange, architect of the nation's antinuclear policy that strained relations with the United States, died yesterday. He was 63.

He died at a hospital in the northern city of Auckland of complications from kidney failure, his family said.

Mr. Lange, a Labor prime minister from 1984-89, defied the United States and other Western allies in 1985 by banning nuclear arms and nuclear-powered ships from New Zealand territory and waters. The ban is still in effect.

He is also credited with giving his nation of 4 million its most radical economic overhaul in an attempt to open its markets. Though he was forced from power in 1989 by his own lawmakers, the center-right National Party that took power the next year continued his economic program.

The son of a doctor, Mr. Lange started his career as a lawyer who championed of the rights of poor. He became a lawmaker in the northern city of Mangere, near Auckland, in 1977. In 1983 he was elected Labor leader and 16 months later led his party to government. He was 41, the nation's youngest prime minister of the last century.

A Methodist lay preacher, Mr. Lange spurned the trappings of official life by not moving into the official premier's residence. Instead, he rented a small apartment in Wellington while his first wife, Naomi, and their children remained in Auckland.

Known for his down-to-earth wit, Mr. Lange said to retiring US ambassador H. Monroe Browne, who owned a racehorse called Lacka Reason, ''You are the only ambassador in the world to race a horse named after your country's foreign policy."

In a debate with nuclear weapons' supporters at Oxford University, Mr. Lange's quips included: ''Lean forward, I can smell the uranium on your breath."

Yet his leadership left his party in disarray. It took nine years for Labor to regain power after its defeat in 1990, a year after Mr. Lange resigned as prime minister citing ill health.

He fell out with a powerful group of ministers when he called for pause in the rapid rate of economic reform. And his nuclear ban put him at odds with the Reagan administration.

Mr. Lange's government also abolished farm and export subsidies and privatized state-run enterprises such as the railroad, the postal service, and telecommunications -- moves that cost thousands of jobs.

After divorcing in the 1990s, Mr. Lange married his former policy adviser Margaret Pope, with whom he had a daughter.

He suffered ill health through much of his adult life.

In 1983, he had a stomach-stapling operation in an effort to lose weight. He was treated for coronary heart disease with multiple bypass surgery. He admitted to alcoholism in 1999, joining Alcoholics Anonymous. In 2002, he underwent chemotherapy for a rare plasma disorder.

In 2003, Mr. Lange won a Right Livelihood Award, known as the ''alternative Nobel," after reportedly having been nominated for a Nobel Peace Prize.

He also was named to the Order of New Zealand, the nation's highest honor, bestowed on just 20 living New Zealanders at any one time.

He leaves his wife and four children.