A US pop star has been caught up in Australia's same-sex marriage debate, with her image being used in an advertisement for the No campaign without her permission.

A photo of Meghan Trainor, whose hits include All About That Bass and NO, appeared in a post that has since been deleted on the Vote NO Australia group's Facebook page.

Beside her face were the words: "My vote is no you need to let it go."

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A fan tweeted Trainor to inform her of the ad, prompting the singer to hit back.

In a series of tweets, she expressed her anger over the incident and urged her fans to "vote yes for marriage equality".

"I've said it before, everyone should be able to love who they want. I support equality, period."

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Vote NO Australia has since deleted the post and posted an apology on its page.

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"It has come to our attention that a meme was posted on the page by a new editor that was not correctly vetted of an opinion of a celebrity," it said.

"Once it came to our attention it was immediately removed.

"We apologise to Meghan Trainor and her support base if this has caused any angst or distress.

"We had no idea who the person in the meme was. It was sent to us by a contributor to the page.

"For the record we note Meghan Trainor supports Marriage Equality and we respect her right to her opinion on the matter."

The Vote NO Australia page is followed by more than 4,000 people, and in its information section says, "It is not fair that husband and wife will become illegal terms and their use regarded as discriminatory against gays".

It goes on to say:

It is not fair that our children will be prevented from calling their parents "mum" and "dad". It is not fair that we cannot say No to this without being called homophobic. It is not fair that we cant live according to our faith. No — we just want the term "marriage" to stay the way it is - between a man and a woman as per our culture, religion and traditions.

Pop culture joins same-sex marriage debate

The incident occurred alongside pop culture media giving prominent coverage to the Australian Government's survey on whether the law should be changed to allow same-sex marriages, as the last day to enrol in time for the vote passed by.

How to enrol You can put your name on the electoral roll or update your details on the AEC's website

You can put your name on the electoral roll or update your details on the AEC's website There is also a dedicated phone line to help answer any questions: 1800 572 113

MTV Australia today replaced its usual programming between 6:00am and 6:00pm AEST with a message asking people to enrol.

MTV Australia's homepage also defaults to the message "It's time to have your say on marriage equality in Australia", with instructions on how to enrol, check enrolment or change address.

Websites Pedestrian TV and Junkee said they would undergo a partial black-out between 5:00pm and 8:00pm AEST, only displaying LGBTIQ content, while HuffPost Australia yesterday asked its readers: "Where the bloody hell are you?"

Key dates in SSM postal survey: August 24 — the final day to register with the AEC if you want to take part in the survey

September 12 — survey forms start being sent out

September 25 — all forms are expected to have been sent

October 27 — forms are strongly encouraged to be returned by this date

November 7 — the final deadline to return surveys

November 15 — results are released

Google's home page in Australia contained a subtle reminder to enrol under the search bar.

Australians who want to have their say in the upcoming same-sex marriage postal survey have until midnight tonight to enrol.

Enrolled voters will begin receiving surveys on September 12, and the Australian Bureau of Statistics (ABS), which is overseeing the survey, says all forms will be mailed out by September 25.

The ABS "strongly encourages" people to send their surveys back by October 27.

Responses must be returned to the ABS by November 7.