Speaking to The People newspaper, the Welsh singer also blasted the long-running series for being more about the sob stories than the talent.
Tom, who will be coaching on the new BBC One series alongside Will.i.am, Jessie J and Danny O'Donoghue, also complained about the show's judges.
“At times it feels The X Factor is more about sob-stories and finding someone who’ll sell a lot of records quickly and then disappear than their singing ability," he said.
He went on to moan: “Every time I see one of these shows I think half the decisions are wrong and it really frustrates me.
“Some of the judges don’t have the experience to be on talent shows – if you’ve only been in the industry two minutes, how can you offer advice?
“I have the experience and I listen to all sorts of music, so the advice I give will be valuable.”
Speaking about signing up for The Voice, which starts on BBC One next month, the 70-year-old explained: “I got fed up with shows like X Factor and thought I better do one myself because the judging has been questionable.
“A singing contest should be about someone’s voice – not PR spin.”
He added: “I’m genuinely excited about The Voice – it’s exciting, competitive and compelling television because it’s all about talent.
“I’ve been blessed over the years to have been able to share the stage with some of the worlds finest artists and I’m really enjoying being part of the team discovering a great new talent."