Support was lowest among older Australians and Generation Y voters, with people aged 35 to 65 most supportive of Australia abandoning the monarchy.

An exclusive ReachTEL poll of more than 2100 Australians, conducted on Thursday night for Fairfax, shows 41.6 per cent oppose the country becoming a republic, and 19 per cent had no opinion on the issue.

Australians for a Constitutional Monarchy national convener David Flint said the findings were a ''time bomb'' for the republican movement, with support among 18 to 35 year olds at 35.6 per cent. More people in this age bracket oppose a republic than support it. Only people aged over 65 had a lower rate of support (30.7 per cent) for Australia becoming a republic.

''That is a time bomb, I believe, for republicans, because you don't have that investment for the future,'' Professor Flint said.

Not only were young people disinterested in a republic, he believed, they were favourable to the monarchy partly because of the star power of the ''young royals'', Princes William and Harry and the Duchess of Cambridge, Kate Middleton.

But Geoff Gallop, chairman of the Australian Republican Movement, said: ''Polls will come and go, but we've been encouraged by the support we've been getting, and our campaign will continue.'' Mr Gallop said higher support for a republic among Generation X and baby boomer voters could be explained by them having participated in the 1999 referendum, and remembering the 1975 constitutional crisis.

The poll was conducted less than a week after Prime Minister Tony Abbott named General Peter Cosgrove as the next governor-general, the Queen's representative in Australia. Mr Abbott said he could ''not think of a better person'' to fill the governor-general role than General Cosgrove. ''Throughout his life, he has demonstrated a commitment to our country and a commitment to service,'' Mr Abbott said. ''He has given service of the very highest order to our country. I am confident that in this new role he will continue to deliver to a grateful nation leadership beyond politics.''

General Cosgrove was roundly endorsed by male voters in the ReachTEL poll, with 61.9 per cent of men saying the decorated veteran was a better choice than Quentin Bryce. Ms Bryce, who five years ago became the first female governor-general, is due to retire next month.

Women were more supportive of Ms Bryce, with 47.4 per cent saying she was a better governor-general, compared with 52.6 per cent of women supporting General Cosgrove.

In November, Ms Bryce used the final Boyer lecture of the year to publicly support the push for Australia to become a republic. Ms Bryce said she hoped the nation would evolve into a country where same sex marriage was legal, ''and where perhaps, my friends, one day, one young girl or boy may even grow up to be our nation's first head of state''.

At the time, Mr Abbott, a staunch monarchist, said: ''It's more than appropriate for the Governor-General, approaching the end of her term, to express a personal view.''

According to the ReachTEL poll, women were less likely to support Australia becoming a republic (with 36 per cent support) than men (with 43 per cent support).