Rokunuz Zaman, who was programme officer for Lepra's Bangladesh project between May 2004 and November 2005, claimed at the hearing that he endured bullying and race discrimination from senior management while working at the Colchester-based organisation.
Zaman alleged that in a disciplinary meeting in October 2005, Lepra bosses accused him of having an affair with the secretary for the charity's Bangladesh office, and that he was subsequently given 15 minutes to resign or be dismissed.
Although he denied having an affair, Zaman said he chose to resign for "family reasons" rather than be sacked for gross misconduct.
Zaman claimed he was subjected to racist comments from the very beginning of his career at Lepra.
He alleged that after he returned from a routine work trip to Bangladesh, he was told by chief executive Terry Vasey that Bangladeshis were "untruthful, very political and complicated, and always out to make trouble".
"This upset me and made me very low in my self-esteem," Zaman told the tribunal. He added that Vasey repeated the comments on Zaman's last day at Lepra. Vasey allegedly came to sit down next to him and said: "You people are very difficult, untruthful and complicated. I don't just mean you; all Bangladeshis."
Lepra's lawyer, Michael Lane, challenged Zaman on whether his statement had been written in his own words. "This is in my own words, but English is not my first language," the claimant replied.
Referring to Zaman's earlier allegations that Vasey and another employee of Lepra had asked discriminatory questions during his job interview, Lane said: "You are not telling the truth about this. None of this happened." Zaman replied: "I would strongly say that is not right."
Lane suggested that Zaman had "a very high opinion" of his own skills and experience. "If Terry Vasey took a tough line, then you disapproved," Lane said.
"Sometimes I had to compromise," Zaman replied.
The hearing, which opened in April in Bury St Edmunds, Suffolk, was adjourned until last week in order to schedule time for a 12-day sitting, which has now been transferred to Stratford in east London (Third Sector, 25 April).
Lepra began as the British Empire Leprosy Relief Association in 1924 to "rid the empire of leprosy". Today it also helps people affected by TB, HIV and malaria in nine countries with a combined population of 300 million.