Rick sings the lead vocals, and this is for sure. Someone joins for the chorus as backing vocals: I cant' tell if Dave or Rog but I'd say David.

As for the authors for music and lyrics I frankly don't know. Both music and lyrics seem much more Wright's stuff than Roger's (Rick doing lead vocals reinforces this point) and books are not clear about this.

__________________
"Don't you know there ain't no devil, it's just god when he's drunk." Tom Waits