Mark Levin says a former Democratic National Committee consultant and onetime Clinton White House staffer should have been a key witness during the House Intelligence Committee's impeachment hearings.

During a special solo edition of "Life, Liberty & Levin" airing Sunday at 8 p.m. ET, Levin pointed to part of a 2017 Politico report on alleged "Ukrainian efforts to sabotage Trump."

"A Ukrainian-American operative who was consulting for the DNC met with top officials in the Ukrainian Embassy in Washington in an effort to expose ties between Trump, top campaign aide Paul Manafort and Russia, according to people with direct knowledge of the situation," Levin said, quoting journalist Kenneth Vogel, who now writes for The New York Times.

Levin said Republicans on the Intelligence Committee had asked to have the operative, Alexandra Chalupa, testify during the hearings. However, the request was shot down by Committee Chairman Adam Schiff, D-Calif.

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"She should have been called as a witness to figure out exactly what her role is," he said. "There are a number of articles about this woman and what she was doing with the DNC, the Hillary Clinton campaign, the State Department and, by the way, met several times at the White House with the so-called whistleblower."

Levin said Schiff's reticence to hear publicly from Chalupa is a symptom of his wider refusal to hear from a number of witnesses considered key by the Republican minority.

"We're not allowed to ask about her," he said. "We're not allowed to ask about the whistleblower. We're not allowed to ask about Hunter Biden."

Instead, Levin remarked, Schiff's Democratic majority was content to "bring in bureaucrats who don't know a damn thing to begin with."

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During the past week's hearings, however, Chalupa came up at least once in Republican questioning of former U.S. Ambassador to Ukraine Marie Yovanovitch.

Republican counsel Steve Castor asked Yovanovitch about the reports Levin referenced claiming that during the 2016 race, Chalupa had meetings with officials at the Ukrainian Embassy in Washington to discuss incriminating information about people associated with the Trump campaign.

Yovanovitch said she did not believe she knew Chalupa. Further, when asked if she tried to investigate those interactions, she maintained this would have been handled in the U.S. since the meetings took place in Washington, not in Ukraine.

The questioning drew a Twitter response from Chalupa, who said she has never been to Ukraine and was not involved in opposition research against then-candidate Donald Trump.

"For the record: I have never worked for a foreign government," she tweeted. "I have never been to Ukraine. I was not an opposition researcher. In 2008, I knew Manafort worked for Putin’s interests in Ukraine. I reported my concerns about him to the NSC in 2014 & sounded the alarm bells in 2016."

Fox News' Brooke Singman contributed to this report.