06/08/2017 2:33 PM AEST | Updated 06/08/2017 4:18 PM AEST

'Incredible Crowd' Descends On Sydney For Marriage Equality Rally

Organisers want a free vote in parliament.

Hundreds of gay marriage supporters have rallied in Sydney as the Liberal party prepares for an emergency meeting to resolve a stand-off on the long-running issue.

Organisers of Sunday's marriage equality rally in the city's CBD estimated up to 600 people attended the event that kicked off around 1pm AEST.

Protesters held placards declaring 'Marriage Equality Matters' and chanted, "What do we want? Marriage equality! When do we want it? Now!".

LGBTIQ activist Sally Rugg told the crowd that the rally was taking place "13 years after John Howard changed the Marriage Act to specifically exclude us".

Those in attendance want a free vote in parliament to decide same-sex marriage, which this week re-emerged as a hot button issue. Several Liberal MPs have threatened to abandon their party's stance on same-sex marriage that mandates determining the issue via a national plebiscite.

By contrast, Labor and the Greens back a free vote in parliament, which whey say would be a cheaper and easier option.

A marriage equality rally in Melbourne is due to start at 2pm local time.

Earlier, Liberal senator Dean Smith told the ABC that a parliamentary vote on gay marriage should happen as soon as possible.

"I will be arguing the parliamentary free vote option as I think that is most consistent with our traditions but more importantly, there is an electoral advantage as it deals with this quickly by the parliament and is settled for all," said Smith, who has drafted his own marriage equality bill.

While parliament does not return from the winter break until Tuesday, Prime Minister Malcolm Turnbull has hastily recalled his party for a special meeting to settle the rift on same-sex marriage on Monday.