X Factor 2011: Jessie J upset Misha B sang Who Are You before her

It may be a platform for aspiring hopefuls to launch their careers, but it's also a showcase for established artists to boost sales during guest appearances.

So Jessie J wasn't too happy that her glory moment of debuting her new song on X Factor tonight was tainted by Misha B - who sang the track two weeks ago.

The Do It Like A Dude singer was invited on the ITV reality series to perform her latest single Who Are You, but the Mancunian got there first by singing it during the sing-off with Kitty Brucknell.

Guest performer: Jessie J sang new song Who You Are on X Factor, but is said to be annoyed that Misha B performed it first

Gothic: Jessie J dressed entirely in black as she performed on the reality show

A source told the Sunday Mirror: 'Two weeks ago when Misha was in the sing-off with Kitty Brucknell, she wanted to sing Who Are You.

'She loves Jessie and sees her as an inspiration so it was a real honour.'

'But Jessie and her camp had wanted tonight to be the first time the track was performed on The X Factor. It was a bit of a mix-up and not really anyone's fault, but Jessie wasn't happy.'

Rising star: Jessie J has continued to have success since winning her Critic's Choice Brit Award earlier this year

The insider added: 'She's too nice a person to say anything to Misha, but if they meet it might be a touch awkward at first.'

But Jessie didn't let the hiccup set her back, belting out a powerful rendition of her song while dressed in an elegant floor-length black gown with revealing lace detail on the upper body.

Before the event, she tweeted: 'Calling all #heartbeats my dEBUT performance of #WHOYOUARE LIVE is TONIGHT on XFACTOR at 8pm on ITV!!! RT'

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There was a mixed reaction on Twitter, with people split down the middle on which rendition was more powerful.

One user of the social networking site wrote: 'I aren't (sic) being funny but I thought Misha B was better at performing who you are than Jessie J,' while another quipped: 'Jessie J had a Diva strop cuz Misha B sung her song on the X Factor, before she did. Grow up Jessie.'

However, one supporter wrote: 'without being horrible Jessie J just showed Misha B how it is done. #whoyouare'

Song thief: Misha sang Jessie J earlier this month when she was saved against Kitty Brucknell

Jessie J revealed who she is rooting for in the final when host Dermot O'Leary quizzed her, admitting: 'Little Mix.'

The 23-year-old formed a bond with the girl band while guest-mentoring with Tulisa Contostavlos in the final round of the auditions at judge's houses.

Luck of the Irish ran out: Janet Devlin was sent home tonight after singing for survival against Misha B

Home time: Janet's rendition of Snow Patrol Chasing Cars was not enough to save her against Misha B

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