They said federal prosecutors in NY say Cohen sought employment in the Trump administration - something Cohen repeatedly denied in the hearing.
Nadler said that Whitaker was "directly involved in conversations about whether to fire one or more US attorneys".
Nadler also claimed that Whitaker "did not deny" that Trump called Whitaker to discuss Cohen's case and personnel decisions surrounding it, as had been reported by the New York Times. "To imply it would imply anything else besides that is really an overreach", Collins said. "Mr. Whitaker said he did not have conversations with the president about Cohen", Collins, who has publicly butted heads with Nadler, told reporters. "But it is jaw-dropping that the acting Attorney General blatantly lied to Congress and he was concerned enough about going to prison that he came back a week later to do clean up".
Whitaker was called to Capitol Hill to clarify his testimony at a combative February 8 committee hearing, during which he denied speaking with President Donald Trump about a federal case involving Trump's former attorney Michael Cohen. He also disputed Nadler's interpretation of Whitaker's potential discussions about the Southern District.
But a staffer for the Georgia Republican who was also in the room and took notes during the meeting did not go that far.
Meanwhile, the chairman of the committee suggested that Whitaker may have had conversations with President Donald Trump about Cohen's legal troubles, claiming that Whitaker "did not deny" the conversations during a private meeting on Capitol Hill.
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However, Nadler did not say Whitaker explicitly acknowledged having conversations with Mr. Trump about Cohen.
But during combative questioning by Democrats, Whitaker was asked by Nadler whether he had "communicated any information" he had learned in briefings with investigators to the president.
"He would not say no", Nadler said when pressed further.
On Wednesday, Republicans on the committee challenged Mr. Cummings to live up to that.
Nadler said after the public testimony that his answers were 'unsatisfactory, incomplete or contradicted by other evidence.' In the letter sent to the Justice Department, Nadler said Whitaker didn't offer clear responses about his communications with the White House and was inconsistent about what questions he refused to answer. Trump has denied those claims.
Cohen pleaded guilty past year to circumventing campaign finance laws when he paid pornographic actress Stormy Daniels $130,000 in hush money before the 2016 election so that the story wouldn't derail Trump's campaign.