Britney Spears is ''as sweet as a lemon'' when judging 'The X Factor' USA.
The 'Toxic' singer has just recently finished filming auditions for the second series of the pop star search show, and boss Simon Cowell says she is not afraid to hold back on contestants who are not up to standard.
Speaking at a press conference in Miami, Simon - who himself has been dubbed 'Mr Nasty' for his cutting comments on the UK version of the show - said: ''Britney is quite mean, which I think you will discover.''
He added Britney and fellow new judge Demi Lovato are harder to please than him or the fourth member of the judging panel, L.A. Reid.
He said: ''They are harder to please than me or L.A. They are very happy giving people a 'no.' They definitely have their own opinions.''
Among the statements Britney has made to contestants during filming have been ''you can't destroy that song, sweetie,'' and ''I want to know who let you on stage''.
Britney - who got her first break as a singer aged just 15 - insists she was tough because she wants to give people a realistic taste of the music business and wants to help them get better as artists and performers.
The 30-year-old pop star is adamant she is ''just a very honest person,'' adding: ''I have done eight tours and I have been in the music industry for a while, and I think being able to give back is really interesting.''
'The X Factor' will return to screens in the autumn.