The presenter, 28, was rumoured to be dating the One Direction hunk, 20, last year after they appeared to be leaving the same building the morning after a night out, but she's confessed she was never romantically involved with him because he's far too young for her.
She told heat magazine: ''I was never seeing Niall. He's a child. The most embarrassing thing about that is that people thought we were together.
''I love Niall, he's lovely. But I'm 28. He's a boy. And he kind of looks like my little brother. So, no.''
Laura - who is reportedly dating 'Scream (Funk Up My Life)' hitmaker Paolo Nutini - has been signed up to present the Eurovision song contest's semi final with BBC Radio 1 presenter Scott Mills.
She is also reportedly taking over from Caroline Flack as the host of 'The Xtra Factor', but she claims she hasn't been offered the job.
She explained: ''My mother actually called me up and was like, 'You didn't tell me you were doing 'The Xtra Factor'!' But listen, I've been in LA for a week, so I have no idea what's going on.''
The actress spoke about raising her 11 year old daughter Matilda in the wake of Heath Ledger's death eight years ago.