The singer mimed Womanizer when she appeared on the ITV show on Saturday.
I dont see the point of Britney anymore, she was rubbish on the show, the Take That frontman, 37, tells the Daily Mirror.
I think shes more famous than she deserves to be now. I dont like her new song either.
'Her old stuff was great but maybe she should have spent more time on this one.
But Gary can understand why Britney, 27, could have been put off by Simon Cowell, 49.
You walk out there and Cowell's just looking at you, he tells The Sun.
'It puts you on edge straight away. Id be bloody nervous.'