A government watchdog group filed a lawsuit Wednesday against the State Department asking for communications of senior officials related to a series of opinion columns by John Solomon in The Hill that have been blamed for fueling conspiracy theories at the center of the impeachment inquiry.

Democracy Forward Foundation, a nonprofit watchdog group, says the Trump administration has failed to fulfill a Freedom of Information Act (FOIA) request for communication between senior State Department officials and Solomon, a former columnist for The Hill whose articles contributed to the ousting of the Ukrainian ambassador and revived accusations that the Obama administration covered up improper dealings of former Vice President Joe Biden, his son Hunter Biden and a Ukrainian energy firm.

The group said its lawsuit, filed in federal court in Washington, D.C., fulfills an urgent public need to determine if senior government officials were complicit in publication of the articles that are at the heart of the impeachment inquiry and could amount to "covert propaganda that violates federal law."

The watchdog group said the State Department has not provided any of the information requested in the FOIA filing within the time period required.

State Department correspondence is included in the lawsuit, which provides receipt of the request and that the department put it on an expedited track to be fulfilled, but that it would be fulfilled on a first-come, first-served basis related to other similar requests.

The lawsuit was filed two days after the State Department letter was sent to Democracy Forward.

The State Department did not immediately respond to a request for comment from The Hill.

Democracy Forward is calling for the agency to provide communications regarding or referencing Solomon from several administration officials who have testified or been referenced in the impeachment inquiry.

This includes acting Ambassador to Ukraine William Taylor, former special envoy to Ukraine Kurt Volker and U.S. Ambassador to the European Union Gordon Sondland, who testified Wednesday.

The lawsuit also calls for communications by Secretary of State Mike Pompeo.

"The Trump administration is unlawfully withholding records that could expose high-level State Department officials using a right-wing reporter to spark the misinformation campaign at the heart of the Trump impeachment inquiry," Democracy Forward Press Secretary Charisma Troiano said in a statement. "The public deserves to know whether the Trump administration violated anti-propaganda laws."

The lawsuit calls for communications, including those on encrypted messaging apps, between Solomon and State Department officials.

Solomon's articles have featured prominently in witness testimony in the impeachment investigation. His articles have been described as being part of a disinformation campaign against former Ukraine Ambassador Marie Yovanovitch, with the purpose of removing her from Kyiv.

Volker testified on Tuesday that he considered the idea that Joe Biden had sought to fire a Ukrainian prosecutor to help his son's business interests was a conspiracy theory. Biden's son Hunter worked on the board of the Ukrainian energy firm Burisma Holdings. Allegations against Biden were also a focus of the Solomon columns.

The impeachment inquiry was sparked by a whistleblower complaint that President Trump during a July 25 call from the White House improperly pressured Ukrainian President Volodymyr Zelensky to open an investigation into the Bidens and their dealings with Burisma, as well as alleged Ukrainian interference in the 2016 election.

The president further disparaged Yovanovitch on the call, describing her as "bad news" and saying that "she's going to go through some things." Trump also told Zelensky that his personal attorney Rudy Giuliani "very much knows what's happening" and said he would direct his lawyer to call the Ukrainian president.

Democrats charge that Trump and his associates conspired to oust Yovanovitch in an effort to put in place more favorable operates in Ukraine to push for the country to interfere in U.S. domestic politics on behalf of the president.

Republicans argue that the administration was following through on policy objectives to root out corruption in that country.

Witnesses in the impeachment inquiry have testified that Giuliani was running a shadow foreign policy in Ukraine and that Trump directed senior officials to "talk to Rudy."

Democracy Forward says its FOIA request "concerns a matter of unprecedented public interest" on whether senior State Department officials aided Giuliani's efforts of a disinformation campaign and "further raises concerns regarding State's compliance with laws banning covert government propaganda."