By Colin Packham
SYDNEY (Reuters) - Australia on Tuesday launched a postal vote on whether to legalize same-sex marriage as a widely watched poll indicated the country would overwhelmingly support such unions.
The non-compulsory ballot, which runs until the end of October, will determine if Australia becomes the 25th country to legalize same-sex marriage, while also healing a rift in the government.
Despite securing 70 percent public support in an Ipsos/Fairfax poll on Tuesday, the issue of same-sex marriage had faced a political deadlock, only broken last week when the Australian High Court gave the all-clear for the vote.
The poll illustrates why parliament should simply vote to approve same-sex marriage without holding the national ballot, said opposition Labor leader Bill Shorten, though he urged a "yes" vote.
"Change in this country only ever happens when people participate in the change," Shorten told reporters in the Australian capital of Canberra. "Please don't leave this change to other people."
The ballot helps Australian Prime Minister Malcolm Turnbull to unite his Liberal-National coalition government, which had been fractured over the issue throughout his two-year tenure.
Some conservative lawmakers threatened to resign if Turnbull did not stick to the public vote, while more liberal members said they would side with the opposition Labor Party to secure same-sex marriage if the PM did not resolve the issue.
Vitriolic allegations have marred the campaign for same-sex marriage, with opponents having launched a contentious "No" campaign advertisement this month that the government immediately rejected as inaccurate.
As the vote is not a formal election, it is not subject to the usual rules on political advertisements, but the government said a new law will probably be passed by the end of the week to prohibit vilification on the basis of people's sex, sexuality and intersex status.
(Reporting by Colin Packham; Editing by Clarence Fernandez)