The Little Britain comic admitted that he is baffled as to why Simon Cowell raised the Life Stories host's profile by signing him for Britain's Got Talent in 2007.
Walliams, now a panellist himself on the ITV show, told The Sun: "I kind of never will understand why Simon decided to make Piers Morgan famous, and now we're all suffering as a result."
However, the comedian added: "He wasn't bad as a judge, but he was like a mini-Simon."
Walliams also appeared to suggest Cheryl Cole's critiques on The X Factor UK lacked substance.
The 40-year-old joked: "I thought Cheryl Cole was great on X Factor, because you didn't really listen to anything she said but you just liked looking at her."