Bars across the United States are shocking customers by serving a controversial cocktail called the Irish car bomb.

Made from Guinness, Bailey's Irish cream, and whiskey, the drink is proving popular in America. Indeed, its name appears in lights outside O'Sheas' casino in Las Vegas where it can be bought for $3.

An Irish poker player visiting the casino told the Sunday Tribune: "I was stunned when I saw an 'Irish car bomb' advertised in lights at a Vegas casino. You'd never see anything like that at home."

The cocktail was reportedly created 30 years ago by Charles Burke Cronin Oat, owner and bartender of Wilson's Saloon in Connecticut.

During his experimenting, adding whiskey to the Bailey's Irish cream made the shot glass bubble up like an explosion, causing Oat to remark that "the IRA just showed up".

The shot of Bailey's and whiskey is dropped into three-quarters of a pint of Guinness. The volatile mixture curdles if not drunk quickly. Some bar-tenders have refused to serve the drink saying the name is offensive.

Irish car bomb ice-cream sundaes and cupcakes are also now the rage in the US. The drink has its own website Irishcarbomb.com. Many other websites also advertise it.

Willie Frazer of IRA victims' group Fair, said: "It is disgusting that IRA car bombs which killed and maimed so many in Northern Ireland are being trivialised or celebrated in this way.

"I would have expected Americans, of all people, to behave more sensitively and responsibly. How would they like it if we developed the Al-Qaeda car bomb, the Twin Towers cocktail, or the 9/11 ice-cream sundae?"

Frazer said the US authorities should clamp down on bars selling the cocktail and the websites advertising it should be closed. "All those who drink this cocktail and see it as a great joke wouldn't think it funny if they were caught in a car bomb themselves.

"I'd challenge them to meet victims of bombings – people who have lost arms and legs and are scarred for life."