DAVID LANGE, the former Prime Minister of New Zealand, was a mercurial, witty and outspoken politician, accused by his opponents of shooting from the lip. He was a political leader who introduced an unlikely mixture of right-wing economic reforms and an adventurous anti-nuclear policy. If he annoyed and confounded both the Left and the Right for being simultaneously against nuclear weapons and for free-market reform, he united pretty much all for his distinctively Antipodean sense of humour.

The economic reforms caused ructions in the New Zealand Labour Party and eventually brought Lange into conflict with his own Finance Minister, Roger Douglas. His anti- nuclear policy, particularly the ban on visits from nuclear-armed or nuclear-powered warships, brought his Government into conflict with Washington and London and brought an end to Royal Navy and US Navy visits.

Such was his unorthodox disposition that he even took part in the Oxford debate, as Prime Minister, to defend his anti-nuclear stance and wore a “nukebusters” T-shirt on a tour of Africa, to the despair of his foreign affairs advisers. His rise in New Zealand politics was meteoric, from backbencher to Prime Minister in seven years — and his impact on New Zealand politics was profound.

Close colleagues said Lange appeared to believe he had a pre-ordained role in life and that this explained his rapid rise to power. Whatever his personal beliefs, he did not pursue his life and policies with a messianic zeal. In fact, he only gave the impression of hugely enjoying himself. The portly schoolboy, who once used his wit and debating skill to keep out of trouble, had obtained a larger audience.

David Russell Lange was born on August 4, 1942, the son of an Auckland doctor. He developed into a Billy Bunter of a youth at school and, according to his mother, developed his bantering style to fend off the inevitable teasing which his figure attracted. At Auckland University he graduated in law in 1966, and then worked for an insurance company and a bank in London.

In 1967, Lange had a fateful introduction to the ideas of the Methodist minister, Donald Soper. As Lange later recalled, he entered Lord Soper’s West London mission looking for free tea and biscuits. He heard words which he felt echoed his own deeply held Methodist conviction, crystallised his own beliefs and resolved some of his doubts. For the young lawyer looking for a meaning and role in life it was a formative occasion.

Lange married a Nottinghamshire woman he had met at the mission, returned to New Zealand in 1968, and spent several years tutoring at Auckland University. He completed a masters degree in law, as well as representing the underprivileged in Auckland courts, often without payment.

In 1977 Lange began his rapid rise to the top of the New Zealand Labour Party when he won the safe Auckland working-class seat of Mangere in a by-election. Two years later he was elected party deputy leader and the next year his supporters failed, by a single vote, to install him as party leader.

His party lost the 1981 election, which in effect confirmed Lange’s succession. It also gave Lange, then an obese 23 stone, a chance to withdraw briefly from the political scene in 1982 for stomach-reducing surgery. As a result he shed several stone, making a dramatic improvement to his image as well as his figure. After the operation Lange said: “It was an important decision — otherwise I would be 28 stone by now.” In 1982 Lange was elected party leader, and in 1984 he defeated the long-time Prime Minister Sir Robert Muldoon in a snap election.

While the Labour Government’s anti-nuclear policy precipitated a row with Washington that led to New Zealand’s effective suspension from the Anzus alliance with United States and Australia, this did not harm Lange’s popularity. The French effectively added to his public support when they sent secret agents to New Zealand in July 1985 to blow up the Greenpeace protest ship Rainbow Warrior in Auckland harbour, killing a crew member. Describing this as “ state-sponsored terrorism,” Lange said that it showed the desperation of nuclear powers.

After winning the 1987 election with an increased majority after an unprecedented switch in allegiance by many former Tory voters, events began to go awry for “Lucky Lange”. He had major clashes with his Finance Minister, beginning in January 1988, when he sidelined Douglas’s proposal for a flat tax of 23 cents in the dollar. This action brought Douglas rushing back from a trip to Europe.

Douglas won the second round in July 1988 after a budget deficit blowout forecast. Lange wanted revenue adjustments so that he could maintain his pledge for a distributive second term — the reward to follow the pain of the austerity restructuring method of the first. Douglas convinced the Cabinet that the deficit had to be controlled by spending cuts.

It was this disagreement that Lange entered hospital complaining of chest pains. An X-ray showed a restriction of the left coronary artery which was cleared with a balloon angioplasty. Emerging from hospital in July 1988, Lange announced his plans to reduce his workload and to take care with diet and exercise.

He survived a vote of no-confidence in the middle of 1989. His response was to stand down as party leader and prime minister — citing ill-health — and he retired from Parliament in 1996. By this time, the conservative National Party was in power, and continuing Lange’s implementation of laissez-faire economics.

Throughout the 1990s, Lange continued to maintain a presence in New Zealand life, in which he was still renowned for his jovial disposition, booming voice and legendary irreverence. He also suffered throughout his life from ill-health, and in 1999 he admitted to joining Alcoholics Anonymous.

He was appointed to the Order of New Zealand in 2003.

David Lange had two sons and a daughter by his first wife, Naomi Campton. He is also survived by his second wife, Margaret Pope, and their daughter.

David Lange, Prime Minister of New Zealand, 1984-89, was born on August 4, 1942. He died of kidney failure on August 13, 2005, aged 63.