A beauty queen whose opposition to gay marriage turned her into an overnight poster girl for America's conservative movement has been stripped of her hard-won tiara, after failing to properly discharge the onerous responsibilities of a reigning Miss California.

Carrie Prejean shot to global prominence after telling judges at the Miss USA pageant in April that "marriage should be between a man and a woman," but was fired on Wednesday for what Miss California officials described as repeated "contract violations."

Her sacking had nothing to do with a media feeding frenzy over recently-discovered topless photos of Prejean, or the revelation that she'd undergone breast enhancement surgery. Neither was it related to tabloid reports that, for all her grandstanding about traditional values, Prejean's mother, Francine, is a lesbian.

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Instead, Donald Trump, the entrepreneur who owns the Miss USA organisation, told reporters that Miss Prejean had simply failed to do her job: refusing, to appear on Larry King's CNN show, or show up at several public events organised by the pageant's sponsors.

"I told Carrie she needed to get back to work and honor her contract," he said. "Unfortunately, it just doesn't look like it is going to happen… Carrie is a beautiful young woman and I wish her well as she pursues her other interests."

Miss Prejean, who will be replaced by her runner-up Tami Farrell, nonetheless claimed that her termination was politically motivated: "None of this would be happening right now if I had just said, 'Yeah, gays should get married," she said.