Andrew Gilbert, 23, said he was singled out by Kathryn Douse, at 22 the Midland Bank's youngest manager, because he was a man.
Mr Gilbert, who was dismissed by the bank after a period of probation at its branch in a supermarket in Heywood, Greater Manchester, is claiming loss of earnings at an industrial tribunal in Manchester.
He told an earlier hearing that Ms Douse was "rude and patronising" towards him and that he was passed over for promotion. He told the resumed hearing that while there was an informal arrangement among staff for carrying out cleaning, Ms Douse one day said to him: "You to mop the floor today".
Ms Douse denied she had discriminated against Mr Gilbert, who was at the time the only man on the staff.
She told Mr Gilbert, of Handforth, Cheshire, who is representing himself at the hearing, that she did not know of thestaff's arrangement, but could not recall ever seeing him cleaning. "The floor needed doing, he was free and I asked him to do it," she said.
Mr Gilbert also claimed that when a female member of staff misplaced her keys she got a "slap on the wrist", whereas he was given two serious verbal warnings for misplacing his.
"I made allowances for everyone," Ms Douse told him in cross-examination. "However, the allowances stop when you lose your keys totally as you did. It was a serious matter."
Ms Douse said he was dismissed for poor performance, a bad attitude and a lack of initiative. He had been late and had breached security procedures over credit cards.
Mr Gilbert accused Ms Douse of "hounding" a previous male employee out of the bank, which she denied. He told her: "You also wanted rid of me because you didn't like working so closely with a man."
The tribunal continues.