Marking the centenary of the divisive plebiscite on Friday, the Australian National University's Professor Joan Beaumont said the electorate showed an extraordinary sophistication in voting down the proposal for compulsory overseas service put forward by Labor prime minister Billy Hughes, despite overwhelming support for the war.

"The 1916 campaign is won by a lot of grass-roots activism in the labor movement and elsewhere," she said. "The quality of the debate was extraordinary."

The result, a 51.6 per cent no vote from an impressive voluntary turn out of 82.5 per cent of voters, led to Hughes being expelled from the Labor Party the next month, but retaining the prime ministership with the support of 24 pro-conscription Labor members and the opposition.

UNSW Canberra Professor Peter Stanley said the no victory came despite the major newspapers of the time backing the move to widen the federal government's conscription powers beyond its domestic boundary, as Britain called for an extra 5500 Australian troops per month.

"The people see that it's them against the government," he said. "It's a powerful moment – in the middle of the war people were asked their opinion."

Professor Beaumont, from the Strategic and Defence Studies Centre, said this contrasted starkly with the passing of conscription laws by non-Labor governments in Britain, Canada and New Zealand.

"Of all of the leaders of the British empire, Hughes was the only one to put the issue to a popular vote, and that's because his own party was split," she said.

The two professors, among four academics who spoke at a National Library of Australia lecture on Friday, agreed that class played a major part in the non-binding plebiscite, popularly known as a referendum despite not involving a constitutional change proposal.

Those in the working class, Irish Catholics or trade union members were more likely no voters, with middle class and Protestant citizens more likely yes, but these lines were clearly crossed, Professor Beaumont said.

Professor Stanley said traditionally conservative farmers were more split on the vote than expected, with many opposed to losing their sons who worked on their properties. Serving soldiers, while narrowly yes voters as a whole, were also less enthusiastic about forcing others to fight overseas than Hughes had expected.

Professor Beaumont said a yes vote would have led to a "very different Anzac legend".

"The legend is at heart a cult of the volunteer – and the very fact you volunteered made you the superior citizen," she said.

A second plebiscite on the same issue, held in December 1917, was also defeated. Both agreed that, unless there was a direct threat such as in 1942, a similar plebiscite would not pass today.