Ansell will be shown on this evening's opening episode impressing at the try outs with a rendition of Queen's 'Somebody To Love'.
Superstar is attempting to find a new great rock talent to play Jesus in the first ever UK arena tour of Tim Rice and Andrew Lloyd Webber's Jesus Christ Superstar.
Spice Girl Mel C, Jason Donovan, David Grindrod and Dawn French will be helping Lord Lloyd Webber cast his next star through various auditions and live shows.
Despite failing to impress judge David Grindrod with his high notes, Lord Lloyd Webber describes Ansell's vocals as "stunning".
After his performance, Ansell told the cameras: "I hope all the panel can see I could be Jesus."
G4 secured a No.1 album in 2005 after finishing as runners-up in the first series of The X Factor.
They went on to release two further albums, before splitting in 2007 over musical differences.
Superstar starts tonight (Saturday, July 7) at 7.25pm on ITV1.
[Photo Gallery - Superstar show 1]