Union J are scared of Ella Henderson's new ''sexy'' image.

The four-piece boyband - who made it to the live finals of 'The X Factor' along with Ella in 2012 - were taken aback to see their ''little sister'' acting provocatively in her music video for her number one single 'Ghost'.

Jaymi, 24, told Digital Spy: ''It does scare me. We remember Ella being 16 and our little sister, and she's in the music video looking sexy.

''I was like, 'Get it off, now! Put some clothes on!'''

Although the boyband - made up of Jaymi, Josh Cuthbert, JJ Hamblett and George Shelley - find Ella's seductive new look hard to accept they admitted they are thrilled for the 18-year-old after her debut track shot to the top of the charts.

Jaymi explained: ''For someone who came sixth on The X Factor to be one of this year's biggest-selling artists is incredible. She's amazing. We're so proud.

''People always put two fingers up to X Factor and say it's s**t, but you can't argue with One Direction, Ella and people like that.''

Jaymi also revealed he's asked Ella to perform at his upcoming wedding to his fiance Olly Marmon - although following on from the success of 'Ghost' he isn't sure she will have the time.

He said: ''I did ask her. She was, but now she's going to be a global superstar I'm not sure if she'll fit it in. That would be a dream.''