Tulisa Contostavlos was "crapping" herself when she did her first live 'X Factor' show.

The 23-year-old singer - who took over as a judge on the series from Cheryl Cole - admits she struggled initially to know what to say and how to critique the acts, and wanted to make sure she didn't "stumble".

She said: "I was absolutely crapping my pants. I just kept thinking. 'You can't make a mistake or mumble your words.' You have 20 seconds worth of constructive criticism and you have to sound like you know what you're on about.

"It's tough. You're under pressure. You're on live TV, you're in front of millions of people. If you even stumble a little bit, people are like, 'Oh she doesn't know what she is doing.' "

However she is quick to deny she has replaced Cheryl as the role of the nation's "sweetheart" because she is too rebellious.

She told FHM magazine: "I've become the nation's little rebel. When you think of the nation's sweetheart you think of someone a bit more elegant and graceful and ladylike.

"When people say to me I'm the new nation's sweetheart I'm like, 'No! That role will always belong to Cheryl!' "