President Donald Trump hired Michael Flynn to be his national-security adviser even after Flynn had informed Trump's transition team that he was being investigated by the FBI over his lobbying work for Turkey, The New York Times reported Wednesday.

The revelation is just the latest in a series of controversies related to Flynn's work on behalf of foreign agents. They include a $33,000 payment from Russia's state-owned news network in 2015, which he failed to disclose on security-clearance forms last year.

A White House spokesman told Business Insider on Thursday that the Times story "is flat wrong. Neither Michael Flynn nor his attorneys told Transition Counsel ‘that he was under federal investigation for secretly working as a paid lobbyist for Turkey during the campaign.’”

But the news raises furthers questions about why Trump was so determined to bring Flynn into his Cabinet and overlook his considerable baggage, which included including a falling-out with the Defense Intelligence Agency and his lobbying work for a Dutch firm linked to Turkey's government throughout the end of 2016. Trump has reportedly stayed in contact with Flynn, urging him to "stay strong" in a private message in April, according to Yahoo News.

"Trump's team knew about [Flynn's] ties to Russia and they knew about his work with Turkey," said Rep. Eric Swalwell, a Democrat who sits on the House Intelligence Committee. "What's most concerning is that it looks like they just didn't care. So you have to ask yourself — were Flynn's prior relationships an asset?"

The developments came as Flynn refused a subpoena for documents from the Senate Intelligence Committee, according to Sen. Richard Burr, the Republican chair of the committee.

Democratic Rep. Elijah Cummings, ranking member of the House Oversight Committee, renewed his call for the White House to release any documents related to Flynn that may aid the committee's investigation into his foreign contacts and payments. The White House has so far declined to do so.

"The White House has been obstructing our congressional investigation, covering up for Michael Flynn, and refusing to provide a single document in response to our bipartisan request. Now we can see why,” Cummings said in a statement.

National-security adviser Gen. Michael Flynn, left, arrives to deliver a statement next to press secretary Sean Spicer during the daily briefing at the White House in Washington, February 1, 2017. REUTERS/Carlos Barria

He said that the committee's chairman, Rep. Jason Chaffetz, "needs to subpoena the White House or let the committee take a vote."

Flynn's time at the White House lasted just 24 days. He was asked to resign on February 13 over reports that he had discussed sanctions with Russia's ambassador to the US, Sergey Kislyak, during the transition. But Trump continued to defend him, going as far as suggesting to FBI Director James Comey the next day to drop the investigation into Flynn's foreign contacts, according to a memo Comey wrote about the conversation.

Trump also waited nearly three weeks to fire Flynn after being warned by former acting Attorney General Sally Yates that Flynn could be vulnerable to Russian blackmail. He also ignored advice by President Barack Obama — who fired Flynn as head of the Defense Intelligence Agency in 2014 — to steer clear of him entirely.

But Trump's family "had a blind spot" for Flynn, who asked Trump's daughter and son-in-law for the national-security adviser position shortly after Trump was elected, NBC reported on Wednesday. He got it, the report said, because of his loyalty during the campaign.

White House officials quickly denied that conversation ever took place, calling it "complete and total nonsense."

"What was it about Michael Flynn that everyone in the Trump orbit wanted desperately to have him in the administration?" CNN legal analyst Jeffrey Toobin asked on Wednesday night. "Why did they keep him?"

Matt Viser, the Boston Globe's Washington correspondent, went a step further: "If Trump took this many risks to appease Mike Flynn and give him such a prominent role, it makes you wonder: What does Flynn have on Trump?"

Reuters reported Thursday that the Trump campaign had at least 18 previously undisclosed contacts with Russian officials during the election, six of which were between Flynn and the Russian ambassador, Sergey Kislyak. The two were trying to establish a "back channel" between Trump and Russian President Vladimir Putin "that could bypass the US national security bureaucracy," according to Reuters.

The White House did not respond to a request for comment.

Flynn has offered to testify before the House and Senate intelligence committees in exchange for immunity from prosecution. The offer has suggested to some legal experts that Flynn thinks he might have information relevant to the broader Russia investigation, which could take the focus off himself.

"General Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit," Flynn's attorney, Robert Kelner, said in a statement on March 31.

Swalwell did not comment on whether the House Intelligence Committee had agreed to Flynn's immunity request. But he hinted that the committee might not need the story that Flynn's lawyer has said he is eager to tell.

"Speaking as a former prosecutor," Swalwell said, "you would only offer immunity to a witness who could provide testimony you could not otherwise obtain."