Former U.S. Attorney Preet Bharara slammed President Donald Trump Thursday in his first public speech since he was fired. 

Bharara spoke at the John Jay Iselin Memorial lecture at The Cooper Union.

During the event, the former U.S. attorney suggested his firing had something to do with his office's jurisdiction over Manhattan, which includes Trump Tower. 

Bharara mocked Trump's campaign promise to drain the swamp in Washington. 

"You don't replace muck with muck," Bharara said. "To drain a swamp, you need an Army Corps of Engineers, experts schooled in service and serious purpose, not do-nothing, say-anything, neophyte opportunists who know a lot about how to bully and bluster, but not so much about truth, justice and fairness."

In November, Bharara met with Trump and said he was asked to stay on as U.S. attorney.

But last month, he was asked to resign as part of a house cleaning of leftovers by the Obama administration. Bharara refused, and he was fired.

He started a new job this week as a distinguished scholar-in-residence at NYU.