Speaking on ABC News' "This Week" in his first televised interview since Trump fired him in March as the top federal prosecutor in Manhattan, Bharara said he believed Trump's calls to him violated the usual boundaries between the executive branch and independent criminal investigators.
"It's a very weird and peculiar thing for a one-on-one conversation without the attorney general, without warning between the president and me or any United States attorney who has been asked to investigate various things and is in a position hypothetically to investigate business interests and associates of the president," Bharara said.
He added that during President Barack Obama's tenure, Obama never called him directly.
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Trump slams 'cowardly' Comey
Bharara's comments came just a few days after former Federal Bureau of Investigation Director James Comey testified at a congressional panel that Trump had asked him to drop an investigation into former Trump aide Michael Flynn and his alleged ties to Russia.
Comey also said he believed he was subsequently fired in an effort to undermine the investigation into possible collusion between Trump's campaign and Russia to influence the 2016 presidential election.
Trump has denied allegations of collusion between his campaign and Russia and said he never directed Comey to drop the Flynn probe.
A White House spokeswoman could not immediately be reached for comment.
Bharara said on Sunday that Trump called him twice after the November election "ostensibly just to shoot the breeze."
"It was a little bit uncomfortable, but he was not the president. He was only the president-elect," Bharara said.
The third call, however, came two days after Trump's inauguration. That time, he said, he refused to call back.
"The call came in. I got a message. We deliberated over it, thought it was inappropriate to return the call. And 22 hours later I was asked to resign along with 45 other people," he said.
Bharara stopped short of saying whether he thought Trump had obstructed justice in his conversations and subsequent firing of Comey.
However, he said he thought there was "absolutely evidence to begin a case" into the matter.
