Foreign Minister Julie Bishop has defected blame onto the Labor party after the first anti same-sex marriage television ad aired across the country last night.

She claimed the "debate would have been over" had the party backed a plebiscite or legislated for same-sex marriage itself.

The ad, created by the Coalition for Marriage, links marriage equality to sex education in schools and features three purportedly concerned mothers.

In an appearance on the TODAY Show this morning, co-host Karl Stefanovic pointed out the reaction to the ad had been heated and was "the very thing we were trying to avoid".

"Let me make two points," Ms Bishop said.

"Had Labor backed our plebiscite legislation in the first place, this debate would have been over last February.

"If Labor had backed same-sex marriage when it was in government, but it didn't, this debate would have been over.

"I think it's up to those organisations, those individuals, who put forward these ads to defend the accuracy or otherwise of their publications."

The controversial ad claims problems may arise in schools if same-sex marriage legislation is passed.

At one point, text is flashed onto the screen which reads: “In countries with gay marriage, parents have lost their rights to choose.”

The final message of the ad reads: “We have a choice. You can say no.”

The ad offers no evidence of its claims.

On its website , the Coalition for Marriage says “removing gender from our marriage laws means removing gender from the classroom.”

Opposition leader Bill Shorten labelled the ad as "total rubbish", telling Fairfax it is "offensive and hurtful to LGBTI Australians and their families".

"This is not freedom of speech. This is freedom to hurt. I just want to tell LGBTI families that they are not on their own. Most people know this is total rubbish."

"The school told my son he could wear a dress next year if he felt like it," this woman says in the ad.

"When same-sex marriage passes as law overseas, this type of program becomes wide-spread and compulsory," this woman says.

"Kids in year seven are being asked to role play being in a same-sex relationship," this woman claims.

The Labor leader told the newspaper he is encouraging Australians to participate in the postal survey and promised to "campaign hard" for a "yes" vote.

Many took to social media following the airing of the ad across various programs overnight.

The Coalition for Marriage is supported by the Australian Christian Lobby, which has been trying to raise $10 million to fight a change in the law and to "protect marriage, children and more".

Coalition for Marriage spokeswoman Sophie York has issued a statement saying millions of Australians are concerned about the consequences of changing the Marriage Act.

"Australian parents have a right to know how a change in the marriage law will affect what their kids are taught at school," Ms York said in the statement.

"The education departments won't tell them. Those lobbying for change won't tell them."

The airing of the ad comes after two prestigious Catholic schools, Xavier College in Melbourne and Sydney's Saint Ignatius College, wrote to parents defending gay marriage, arguing the sacrament must evolve with the times and that the Catholic Church understands marriage stretches beyond procreation.

That statement came days after Melbourne Archbishop Denis Hart urged Catholics to vote against change in the upcoming postal survey on gay marriage for the "health and future" of society.

Equality Campaign executive director Tiernan Brady told News Corp Australia the "ad is disgraceful in its dishonesty".

The City of Sydney will spend almost $100,000 in support of marriage equality after councillors voted unanimously to push for 'Yes'.

"Actively and visibly supporting a 'yes' vote will send a strong message to LGBTI people," Sydney Lord Mayor Clover Moore said in a statement on Wednesday following Tuesday night's council meeting.