31/01/2016 2:33 PM AEDT | Updated 15/07/2016 12:51 PM AEST

Bill Shorten Wants PM To 'Get On With' Marriage Equality Reform

Daniel Munoz via Getty Images
SYDNEY, AUSTRALIA - SEPTEMBER 24: Australian Opposition Leader Bill Shorten during a media conference at Tank Stream Labs on September 24, 2015 in Sydney, Australia. Bill Shorten outlining Labor's plan for a smarter, more prosperous Australia. (Photo by Daniel Munoz/Getty Images)

Opposition leader Bill Shorten has called on Prime Minister Malcolm Turnbull to stand by his convictions on marriage equality and allow federal MPs a conscience vote on the issue in parliament.

Speaking at the Midsumma festival in Melbourne, Shorten said if elected a Labor Government would allow MPs to vote with their conscience on same-sex marriage within 100 days of taking office.

He urged Turnbull to abandon plans for a national plebiscite expected to cost about $160 million.

"Everyone knows that the people who want to delay marriage equality and support the plebiscite are the opponents of marriage equality," he told the event.

"What we want on marriage equality is the old Malcolm Turnbull, not the new Malcolm Turnbull. What we want is Malcolm Turnbull the conviction politician."

He called on the coalition to "get on with" legalising gay marriage.

"We'll have true equality in this country and we'll save the taxpayers $160 million of taxpayer money," he said.

"Let's make marriage equality a reality now."

The call from Shorten comes after ongoing debate about the merits of a national vote to decide the long-running issue.

Labor backs a conscience vote in parliament but a number of conservative politicians like Cory Bernardi oppose reform and have even signalled that they might oppose legislative change irrespective of the outcome of a plebiscite.

Earlier this week, 11-year-old Isabella Mills -- who has two gay parents -- gained traction online when she told the Prime Minister that the same-sex marriage plebiscite was a waste of Australian taxpayers' time and money.

Mills said she "was struggling to see the point" in the plebiscite, set to be held in 2017.

"That 160 million dollars that you are willing to waste on a pointless plebiscite is totally unnecessary. I mean, the public has already expressed their views and made it quite clear that they want same-sex marriage for Australia," Mills said.

"I may not be the Prime Minister, but even I know that Australians could use that money elsewhere.

"If an 11-year-old girl can see that, why can’t you?"