Speaking on The Xtra Factor to hosts Caroline Flack and Olly Murs, Mulhern said that his least favourite performance last night (December 1) came from 24-year-old Arthur.
Mulhern said: "I've not been a big fan of his from the start," adding: "But tonight he did better than he's done before, I think the standard tonight has been better than in any other show."
Mulhern then drew comparisons to previous winner Cardle, saying that Arthur reminded him of the 'When We Collide' singer.
Flack then asked whether he thought Arthur had qualities that Cardle didn't possess.
The magician and presenter then replied: "No, I don't."
Mulhern also predicted that if Christopher Maloney were to go through to next week's final, he would win the show.
Watch James Arthur perform 'One' on The X Factor below:
Photo gallery - The X Factor semi-final week:
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