Simon Cowell was ''hurt'' when the Spice Girls refused to sign to his record label.

The music mogul regrets not being quick enough to sign the girl band before they found global fame and sold over 80 million records worldwide.

The band - which included Victoria Beckham, Mel C, Mel B, Emma Bunton and Geri Halliwell - were catapulted to the spotlight in the 90s following the release of their debut single 'Wannabe', which was succeeded by a long line of hits.

In an interview with Jay Leno on 'The Tonight Show' on Monday (09.12.12), Simon said: ''What can I admit to? Spice Girls was probably my biggest mistake. I knew they were going to big and I offered them a deal but I was just too late on the deal and they didn't want to sign to me, that kind of hurt at the time.''

Simon also admitted he wasn't keen on signing Irish boy band Westlife because he thought they were ''ugly'', but he had a change of heart after a second audition.

He said: ''I quickly put together another group. Well another group auditioned for me. They were called Westlife. When they first came along they were the ugliest boyband in the world. So seriously you couldn't get uglier. I said to the manager at the time, 'Forget it.' Then he re-auditioned but one of the ugly ones dyed his hair blonde for the second time I saw them and he got back into the group.

''I didn't recognise him but it all worked out fine. They sold about 50 million albums or something so it all worked out well enough.''