Isabel Sitz, a former executive director for Oppenheimer Europe, told the London Central Employment Tribunal that her boss called the Irish "lying, cheating time-wasters."
Sitz claims she was left a "broken woman" after the majority of her accounts were given to male colleagues and that she was forced out of her job because of the sexism.
She claims male colleagues frequently referred to Oppenheimer as “bunga bunga securities" in reference to Silvio Berlusconi's sex parties.
She is suing Oppenheimer for unfair dismissal and sex and race discrimination.
The Irish Times reports that she told the tribunal that she was pushed off to the side in July 2009, after the appointment of new chief executive Max Lami, who gave the best accounts to the men he hired.
Sitz taped another of her bosses, Robert Van Den Bergh, describing the Irish as "lying, cheating, stealing, time-wasters" and telling her the accounts were being given to male colleague Jonathan Todman because he could bond with clients.
"He went on to explain it is mostly about beer and rugby in Ireland and so he thought I should be removed from the Irish accounts and they should be given to Mr Todman who could take the clients to rugby matches.”
Mr Van Den Bergh denied the claims that the “unfair and disparaging comments about the Irish is symptomatic” of the way his “prejudices” influenced him, and went on to say his comments were a joke to avoid hurting Ms Sitz feelings.
“I could do one of two things; I [can] tell her that as far as Ireland is concerned, and these are two things which for a broker are probably the worst things you can hear in your life, that you are irrelevant and unknown.Or I could do what I probably in effect did, [which] is make a bit of a joke about it, saying they are not the right kind of people for you, you are better than that,” he told the tribunal.
The Spanish-born banker also claimed she was told she had a "verbal problem" and that she was not British enough.
Left with only four accounts by 2012, she was forced to take a £80,000 wage cut, reducing her salary to only £15,000 a year. She was dismissed from the job in June after signing off work sick with stress.
The company is denying Ms Sitz claims, with Mr Lami making a statement to the tribunal that Ms Sitz lost her job because her "core client base had abandoned her" and that she was "caught up in a fantasy of her own making."