Mr Trump, a businessman and philanthropist, described the lady as having “emotional problems”. Speaking to far-right American news website Breitbart, Mr Trump said: “It was purely a disgusting act by somebody who clearly has emotional problems. “For a party that preaches tolerance, this once again demonstrates they have very little civility.” He added: “When somebody is sick enough to resort to spitting on someone, it just emphasises a sickness and desperation and the fact that we’re winning.”
The employee was detained and questioned by the US Secret Service but was later released after Mr Trump declined to press charges.
The incident happened at The Aviary at Chicago’s Fulton Market and the employee has since been placed on leave by the bar.
The Aviary responded in a statement confirming the “unfortunate incident”.
They said: “Last night an unfortunate incident occurred between an employee at The Aviary and Eric Trump. We did not witness the incident and we are just beginning to learn the details.
“What is certain is this: no customer should ever be spit upon. We have not yet spoken with the employee but our HR team has, in the meantime, placed her on leave. We will not discuss internal HR matters beyond this statement.
“More broadly, the online discussion about the incident is troubling. Hundreds of people are calling for the demise of our business, threatening our employees, and posting fake reviews… they are wrong to do so based on the actions of a lone individual.
“So too, however, are those people wrong who are praising this as an act of civil disobedience. We have voices and the means to be heard.
“A degrading act lowers the tenor of debate. To some it might feel good, but it is unlikely to serve any larger purpose.
“We hope this incident can, at least, serve to illuminate the current absurdity of the discourse in our politics.
“As fellow Americans and citizens, we should all aim higher.”
Anthony Guglielmi, a spokesman for the Chicago police department, confirmed officers had helped the Secret Service in response to the matter.
A source told Breitbart that the employee had “murmured inaudibly something that sounded like it was anti-Trump”.
Officers escorted her out of the venue in handcuffs but she has now been released from custody.