Opponents of same-sex marriage in Australia have aired an ad during the country’s biggest gay pride festival.

The clip opposing same-sex marriage, which was paid for by the ‘Australian Marriage Forum’, aired on Channel 7 and 9 yesterday, while the Sydney Gay and Lesbian Mardi Gras was under way.

In the ad viewers are urged to “think of the child” on the impact of same-sex marriage, with a parent saying: “You hear a lot about marriage equality, but what about equality for kids?”

Anti-gay Christian activist Dr David van Gend adds in the clip: “Childen have an equal right wherever possible to both a mum and dad.

“So-called marriage equality forces a child to miss out on a father. That’s not equality for the kids who miss out, that’s not marriage.”

The timing of the ad has led to an angry backlash from gay rights groups, who accused the group of trying to ruin the gay pride celebration.

According to the Sydney Morning Herald, broadcaster SBS has pulled the ad, telling the group: “Our review board has instructed that SBS has the right to choose what ads we run, and I’ve unfortunately been instructed to advise you that we choose not to run this TVC for the Marriage Forum during the Mardi Gras telecast.”

Rodney Croome of Australian Marriage Equality said the ad was “actually harming the many Australian children being raised by same-sex couples because it defends discrimination against their families”.

Australia currently bans same-sex marriage, despite a public majority in favour.

Liberal Prime Minister Tony Abbott remains a strong opponent of same-sex marriage, though he has faced pressure to allow a free vote on the issue.