Viewers of X Factor: The Band have begged for former winner, Leona Lewis, to be made a "permanent" fixture on the hit talent show after impressing fans with her guest appearance on Wednesday.

Leona, 34, joined Simon Cowell and Nicole Scherzinger for the second round of auditions for the X Factor’s latest spin off show, The Band – and left fans mesmerised by her brutal honesty.

Sitting alongside Pussycat Dolls star Nicole and music mogul Simon, Leona watched on as the successful auditionees from the first round had the chance to perform again, this time in Birmingham.

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“Leona Lewis needs to be a permanent judge on any future X Factor thank you #XFactorTheBand,” one online user tweeted.

Another chimed in, “Leona Lewis really one of the best judges this shows ever had #XFactorTheBand.”

A third hinted that Leona makes a better judge than some of Simon’s previous choices – including Robbie Williams’ wife Ayda Field – who starred on X Factor last year.

“Leona Lewis is already a better judge in 15 minutes than Ayda Williams was over a 16-week series. #XFactorTheBand,” tweeted one fan.

READ MORE: LEONA REVEALS HEARTBREAKING MOMENT FROM HER WEDDING

Leona – who has had some judging practise on America’s Got Talent – was labelled “fearless” on Twitter for calling out one of the girls for forgetting the lyrics to Spice Girls.

“You can’t not sing the right Spice Girls lyrics. It’s a travesty,” she said to Nicole Scherzinger after Chiara King made the mistake on stage.

Despite her seemingly harsh comments, Leona knows more than anyone how it feels to be on that side of the table – after she auditioned for X Factor in 2006.

While X Factor: The Band has proved popular so far, the show’s “rushed” format caused some confusion earlier this week, with fans in uproar about the fact it will all have finished by Sunday.

“I quite like the concept of X Factor: The Band but it’s so rushed,” said one fan on Twitter. While another said, “I just want a proper Popstars: The Rivals 2.”

During the week Simon, Nicole and a selection of guest judges will narrow the contestants down to form two bands – a girlband and a boyband – who will then compete to win the show on Sunday.