The brewer filmed five ads for its Spitfire ale featuring its brand ambassadors, comedy duo Alexander Armstrong and Ben Miller, as RAF pilots.
ClearCast, the organisation which clears ads for TV, accepted four but refused permission to air one.
In the ad Armstrong, host of TV quiz show Pointless, says to a Polish soldier: "Listen blud, is you like one of them geezers that's like a Pole from Poland or Russia or something place like that?"
General Vladimir Zhigorski says: “I am General Vladimir Zhigorski, Supreme Commander in Chief of free Polish forces, yes.”
Then Armstrong says: “Only my nan's patio needs doing and I thought we could do, like, a deal for cash?”
Miller then explains to Armstrong that it is “the Paddies what does the building isn’t it?”
ClearCast said: “The proposed script depicted Polish people in the UK in a way that we felt could cause offence.”
The brewer said it was surprised that its “absurd” and “tongue-in-cheek” ad had not been accepted, adding: “The Armstrong and Miller RAF pilot characters are the focus of each advert and their stereotypical perceptions and street vernacular is intended to be the comical subject rather than the subject matter itself.”
But Jennie McShannon, chief executive of the Federation of Irish Societies, said: “It is disappointing to see once again outdated and unfunny stereotypes being used to sell products.
“In our view this ad reflects badly on consumers of Spitfire, as if they will find these tongue_in-cheek assumptions about Irish and Polish people funny.
“Tongue-in-cheek means not to be taken seriously. Where does Spitfire draw a line?”
The other four ads will run on TV from July.