US Attorney Preet Bharara’s office has filed a scathing lawsuit against the city’s Department of Transportation — accusing it of systemic racism under its previous commissioner.

Black employees of the fleet services division were called “n—ers,” “monkeys,” and “gorillas” — and white bosses demoted them and kept them from getting promotions and overtime, says the suit filed Wednesday that seeks damages for victims and changes to its practices.

The trouble started in 2007, when a newly-promoted white executive director demanded that his second-in-command demote a black assistant supervisor.

When the employee repeatedly refused, the boss threw a tantrum, took the black man’s computer, and rerouted phone calls away from his office.

And when another black worker who asked for a cell phone, the boss refused to give him one, and instead handed one to a white worker with less seniority.

“That n—er gets nothing,” the exec director said.

That boss was pushed out in 2010, and a new executive director brought in. While that boss was less overtly racist, he started a practice of promoting mostly whites and also refused overtime to black employees, claims the suit.

City DOT officials said they have been working with the Equal Opportunity Office to make sure similar racism does not happen again and that they are willing to compensate the victims.

“Since being made aware of DOJ’s investigation in late 2015, NYC DOT and the Corporation Counsel have been working with DOJ to reach a settlement, which will include financial remediation where appropriate,” said DOT spokesman Scott Gastel. “In addition, DOT has made administrative structural changes to its Fleet unit and enhanced its internal EEO monitoring.”