One could be mistaken for thinking it is Mardi Gras time on Sydney's Oxford Street with the many rainbow flags lining the street, but it is actually just the beginning of the City of Sydney's "vote yes" campaign.

To support same-sex marriage, 260 rainbow "vote yes" banners will be flown across the city following unanimous support from Labor, Liberals and Greens.

The council voted to give $110,000 to the cause.

As well as flags, the city will send mail outs to encourage a "yes" vote and promote "yes" campaign activities through their communication channels.

Lord Mayor Clover Moore has been a long-time public supporter of same-sex marriage. ( ABC News: Philippa McDonald )

The council also agreed to extend its accommodation grant to Australian Marriage Equality for the use of the Equality Shop at 122 Oxford Street, vacant kiosks in central Sydney and other venues until November.

Lord Mayor Clover Moore said the criticism toward the council's stance has been scathing, but the support she has received outnumbers the critics.

"The city of Sydney is having its say," she said.

"We still have the largest number of LGBTI people in Australia living in our city.

"Overwhelmingly the response has been incredibly positive and supportive — we have had 23 opposing emails but hundreds and hundreds of supportive ones.

To those who have argued the money for the campaign could be better allocated, Ms Moore responded: "Well I think the $122 million of the Federal Government's spending on a non-binding voluntary survey could have been better spent".

Council support important for some, alarming for others

Alex Greenwich said councils in Australia have been some of the biggest supporters of same-sex marriage. ( ABC News: Philippa McDonald )

Independent MP for Sydney and co-chair of Australian Marriage Equality Alex Greenwich said it means a lot to have the council's backing.

"Councils understand this reform is about the people they represent," he said.

"From the Shoalhaven Coast, through to councils in Noosa and from Fremantle, through to councils on the surf coast of Victoria, councils have been standing up for their gay and lesbian constituents."

However, the anti-same-sex marriage movement said what the flags and campaigning promote marks the beginning of the end.

David van Gend is against the council using public money to encourage people to vote a certain way. ( ABC News: Philippa McDonald )

The Coalition for Marriage's David van Gend said politicians should not use public money to tell taxpayers how to vote.

"If we vote yes to overturn the meaning of marriage so much more changes...it will change what your children are taught at school in the LGBT safe schools education," he said.

"This is a foretaste for people in Sydney and the country of what will happen if we give that intolerant minority of activists the power that comes with gay marriage law."

