The 45-year-old pop star – whose fierce rivalry with the former Oasis frontman dates back to the 90s – is currently appearing at the Encore Hotel in Las Vegas, where he encouraged his fans to send any negative feedback of his performance to Liam.
Speaking at the end of his set, the ‘Angels’ hitmaker quipped: "If you have enjoyed the show, I have been Robbie Williams. And if you haven’t and you are upset about anything, I have been Liam Gallagher.
"In fact, if you want to start a hashtag, you can put ‘Liam Gallagher was s**t tonight’, if you want."
Prior to taking aim at Liam, Robbie also lambasted the American audience for his lack of success Stateside.
According to The Sun on Sunday newspaper, the award-winning pop star – who is married to actress Ayda Field – told the crowd in Vegas: "Why didn’t you tell my f***ing friends about me? And I am sorry it has been so long since I last saw you, my North American friends.
"We are kind of planning on doing a pointless tour of North America – no album to promote, no country to break, apart from coming to say hello to you guys. Shall I do that?
"Go and tell your friends about me. I want to be famous in America. I do not want to infamous in America for not being famous in America.
"I want Ellen DeGeneres to know who I am.
"I wondered if you Americans knew some of my songs? I go all around the world entertaining. I am a global f***ing phenomenon, except in America. F***ers."