Watson, who held office for four months in 1904 at the head of the world's first social democratic national government, was almost certainly not the British subject he claimed to be in order to sit in the Commonwealth parliament, to which he was elected at the first election in 1901.

While Watson had claimed his father was a British-born-born miner George Thomas Watson (to whom his mother was later married), historical records show that Watson was born John Christian Tanck in April, 1867, in Valparaiso, Chile, to a Chilean national of German descent, Johan Cristian Tanck, and a New Zealand-born mother, Martha Minchin.

Tanck was chief officer of the brig Julia, which had arrived at Port Chalmers, New Zealand, from Talcahuano, Chile, in December 1865; he married Martha at Port Chalmers on January 19, 1866; they departed in the Julia for Guam on February 2.

The couple separated in 1868 however and Martha returned to New Zealand with her son, marrying George Watson in 1869, and made her 22-month-old son part of her new family.

This all came to light long after Watson's political career. He resigned as Labor leader in 1907 and from Parliament in 1910.

But much historical haze surrounded the details of his birth and, with it, the vexed issue of citizenship. Watson's second wife would tell a story that became family folklore that his mother, heavily pregnant on a ship skippered by George Watson, had the vessel sail out of Valparaiso into international waters for the birth so her son would have British nationality. Indeed, when Watson himself married in 1911, after he had left politics, a newspaper, the Lone Hand, reported that "like many other good Australians, Mr Watson is a New Zealander by birth".

In 1993, I tracked down Watson's daughter (Watson had died in 1941), Jacqueline Dunn, who told me her mother was always insistent her father had been born at sea, not in Chile but in international waters.

The issue had arisen after a visit by the then Chilean president, Patricio Aylwin, who, with Australian prime minister Paul Keating, unveiled a memorial in Parliament House, listing Watson's birthplace as Valparaiso, Chile.

The former Labor minister, the late Al Grassby, in a biography of Watson, written with the help of a Chilean journalist, Silvia Ordonez, concluded that Watson "almost certainly" was not a British subject, but added that in those days "citizenship was a looser concept than it is now". In The Man Time Forgot (1999), Grassby and Ordonez point out that his actual paternal genealogy was not publicly known during his life and it is unclear whether he was even aware of it. However, the writers are adamant that Watson's mother "went to considerable lengths to invent a British pedigree".

While Chris Watson was certainly the most high-profile politician to have fudged, knowingly or otherwise, details of his citizenship, the most brazen by far was King O'Malley, credited as the founder of Canberra and the father of the Commonwealth Bank.

O'Malley had been a travelling insurance salesman in the United States before arriving in Australia in 1888, almost certainly having been born in the US. But he claimed to have been born in Quebec, Canada, which would have made him a British subject and, as the rules then stood, eligible for parliament.

But over the years in what was a colourful career, O'Malley's story was embellished from time to time. Records show he was born in Valley Falls, Kansas, in 1854 (although in his own account, even the year varied). In one account he gave, O'Malley insisted his parents were British citizens resident in the USA and, as his mother went into labour, she crossed the border into Canada so he could have British nationality. (Never mind the fact that Valley Falls, Kansas, is nowhere near the Canadian border).

With tongue firmly in cheek, one of O'Malley's biographers, Arthur Hoyle, in King O'Malley: The American Bounder, observes: "So, by chance, and by a distance of a few hundred yards, King O'Malley was deprived of the opportunity to become President of the United States."

O'Malley died in 1953, the last survivor of the first Commonwealth Parliament. But by then he had abandoned the lifelong pretence, writing in a letter to the widow of a former political colleague: "I am an American."

Dr Norman Abjorensen, of the ANU Crawford School of Public Policy, is the author of The Manner of Their Going: Prime Ministerial Exits in Australia.