One of London’s most senior female executives described Merrill Lynch as “institutionally sexist” at an employment tribunal hearing expected to last up to 16 weeks.

Testifying before an employment tribunal at Croydon, south London, Stephanie Villalba said that, in order to advance at the bank, it had been “necessary to try to disregard any acts of discrimination against me, and focus on achieving brilliant results”.

Ms Villalba told the tribunal that Merrill Lynch “has no process for monitoring equal opportunities … promotion and pay are at the discretion of senior managers, almost all of whom are male”.

She is seeking £7.5m for sex discrimination, unfair dismissal and unequal pay, in what is the biggest sex discrimination claim ever to be brought before a UK employment tribunal.

Merrill Lynch denies the claims, and says Ms Villalba was removed as head of the firm’s private client business in Europe because of “record losses” in the region.

Ms Villalba countered that no financial goals had been set for her position in 2002. She said the her boss, Raymundo Yu, had made it clear that the work she was doing at that time was to pave the way for later profitability.

Speaking in a clear, matter-of-fact tone, she today told the tribunal that she had been highly rated by her superiors at Merrill Lynch, and a talent search for managers to promote within the international private client business found her to have “high potential”.

This process resulted in a promotion in spring 2002 but she said that, later in the year, Ausaf Abbas, a male executive with less experience, was installed as her superior.

Ms Villalba said she suffered “intolerable discrimination” from Mr Abbas. “Aysaf bullied, belittled, undermined and underpaid me,” she said.

She was forced out of her job in July 2003, she added.

“Once a woman was targeted as a threat, a man could get a lot of support from other men by saying that the woman was either ‘high maintenance’ or a ‘bitch’,” she told the tribunal.

“By contrast, a man behaving in a similar way would be described as ‘detail oriented’ and ‘assertive’. Once this started, the woman would be boxed into a vicious circle. She could not complain, and yet she could not advance.

“I recall instances when I have been told I would have been given a job if it had not been the manager’s view that a particular male in the group would not feel comfortable working for a woman.”

Ms Villalba’s case comes after a series of sex discrimination claims were made against Merrill Lynch in the US. Around 900 women made claims against the bank, which has paid out more than $100m (£54m).

In April this year, Hydie Sumner, a claimant who did not settle, was awarded $2.2m in a case relating to her work as a Merrill Lynch broker between 1991 to 1997.

The ruling, the first to find “a pattern and practice” of discrimination by a major Wall Street firm, followed five days of evidence analysing Merrill’s hiring, promotion and pay practices.

The tribunal hearing Ms Villalba’s claim is expected to last for up to 16 weeks.