X Factor husband and wife judging duo, Natalia Kills and Willy Moon, have walked off the show today after learning that “numerous contestants” had not been singing their own music, but in fact songs they had copied from influential popular artists.

While it was common knowledge to many that contestants – from Sarah Spicer to Steve Broad – had not been singing their own songs, both Kills and Moon – neither of whom have real names – said they were “totally unaware” until last night, when contestant Joe Irvine sung Cry Me a River, originally written in 1953 by Arthur Hamilton.

At the conclusion of the song, judges Melanie Blatt and Stan Walker gave Irvine a standing ovation, but Kills was furious, and Moon looked perplexed.

“Hold on a minute,” said Moon, raising his hand to silence applause. “That’s not your song, is it?”

“It’s the song I chose,” replied Irvine.

“No, no, no, but it’s not a song you wrote, is it?” pressed Moon.

“Well, no.”

“And you’re not the slightest bit ashamed of that?”

Kills interjected to tell Irvine he was a “disgusting human being” who had brought “shame and disrepute” to a show “otherwise without incident.”

According to X Factor executive producer, Andrew Szusterman, it was only this morning, in the aftermath of filming, that Moon and Kills were made aware that the show’s entire premise was based on ordinary people singing songs they could never have written themselves.

“Yes, I think they were quite shocked to hear that,” he said.

“Look, how was I to know?” complained Moon on The Edge this morning. “Nothing was ever said about this to me. If I’d known about it I would never have accepted the job in the first place.”

“Couldn’t you just hear, though, that they’ve been singing popular music?” asked the Mike part of Jay-Jay, Mike & Dom.

“Well of course not,” he replied. “People expect me to somehow know all this music. I don’t listen to this music. I only listen to Willy Moon.”

In a joint statement this afternoon, Moon and Kills confirmed that they would be stepping down from X Factor, effective tonight, in protest of what they call “flagrant plagiarism.”

Stan Walker, who made a name for himself in similar circumstances by plagiarising his way through Australian Idol, described his fellow judges’ decision as “dum.”

Walker said he had no other words or letters to add, but had recently learned the word “bridge” and thought that was “pretty interesting, not going to lie.”

Despite his principled stand today, Moon has himself faced criticism in recent weeks from some who claim he stole his name from popular astronomical body The Moon.