X Factor judge Cheryl Cole is at the centre of a judging row after it was emerged she voted an old friend through to the Boot Camp stage of the show.

The 25-year-old Girls Aloud singer praised Austin Drage as 'so soulful' and gushed: 'If that's not your best, I'm excited to see what is.'

But unknown to viewers, Austin, 21, met Cheryl four years ago when his boyband 5Boyz toured with Girls Aloud.

Cheryl even dated his bandmate Brett Warren.

An X Factor insider said: 'He had an unfair advantage. They're pals - it seems obvious she'd put him through.

'In the interests of fairness they should have admitted their friendship.'

Judging row: Cheryl Cole is at the centre of a row after it was revealed that she put an old friend through to the Boot Camp round of the X Factor

The pairs previous acquaintance was kept secret from viewers as the 25-year-old judge voted the Essex singer through to the pivotal boot camp stage of the reality TV show.

After he sang a version of Boyz II Men's hit End of the Road, she said: 'I'm shocked. So soulful your voice was, you hit every note. I don't think we've heard the best from you yet and if that's not your best, I'm very excited to see what is.'

Dannii Minogue and Simon Cowell also backed Drage, while fourth judge Louis Walsh was away.

But a show insider blasted bosses for not revealing their friendship.

Old pals act: Cheryl called Austin's voice 'soulful' but didn't let on that they met four years earlier when she was dating a member of his old boyband

One source told The Mirror: 'Cheryl and Brett weren't in a serious relationship but saw each other quite a bit for a few months.

'Brett and Austin were in the band, So Cheryl and Austin's paths crossed on social occasions as well as during gigs.'

However show chiefs insisted there was nothing improper about Cole's relationship with Drage and pointed out that he would have gone through even without her support.

Austin Drage kneels, right, in the red vest with former boyband 5Boyz. Shaven-headed Brett Warren who dated Cheryl is seen standing, centre

However, a spokeswoman for the television show denied Cheryl had had a relationship with Warren, or even knew Drage.

In a statement she said: 'Austin was in a boyband 5Boyz, which we have always been aware of.

But despite Girls Aloud once appearing on the same billing at a show one night, Cheryl has never met nor had a friendship with AUstin, nor has she ever had a relationship with former 5Boyz member Brett.'

Drage was also on last year's X Factor but did not make it through the first stage to Boot Camp, where contestants are whittled down until the final 12 appear in the live stage show.

Cole was in tears days before when she admitted knowing another contestant on the show.

She met wannabe Nikk Mager, 24, seven years ago on Popstars: The Rivals, the show that launched her career while Nikk failed to make the grade.