A conservative watchdog group is suing the Justice Department to find out if former FBI Director James Comey “coordinated” with special counsel Robert Mueller before Comey's appearance before Congress.

Judicial Watch wants “all records of communications” between Comey and the Justice Department, which would include communications to Mueller, in the run-up to Comey's appearance before the Senate Intelligence Committee in June. Congressional investigators wanted information on Comey’s firing by President Trump, as some lawmakers suspected the move was an attempt to impede a federal investigation into whether his campaign coordinated with the Russian government’s cyber attacks against the Democratic party in 2016.

The Justice Department missed a deadline to release the documents voluntarily under the Freedom of Information Act.

“It would be a scandal if Comey coordinated his Senate testimony with Mr. Mueller’s special counsel office,” Judicial Watch President Tom Fitton said Tuesday. “That we have had to sue in federal court speaks volumes.”

The document request is based on a Fox News report that Comey “closely coordinated” with Mueller, who was appointed to lead the Russia investigation in order to ensure an independent probe took place following Comey’s ouster. Mueller’s investigation also reportedly includes a review of whether Trump attempted to obstruct justice. Comey refused to offer his opinion on the matter during the hearing.

"That's Bob Mueller's job to sort that out," Comey told lawmakers.

At the time, a Fox legal analyst argued that Comey and Mueller were right to communicate in advance of his appearance. "It would be unheard of for a prosecutor to allow his star witness to testify before Congress without heavy coordination," Fox News’ Andrew Napolitano said.

Mueller has received intensifying criticism from some Republican lawmakers who argue that his long-standing friendship with Comey renders him unsuited to lead an investigation that pertains to Trump’s decision to fire Comey from the FBI.

“No one knows Mr. Mueller’s true intentions, but neither can anyone dispute that he now clearly appears to be a partisan arbiter of justice,” Rep. Trent Franks, R-Ariz., said in August. “Accordingly, the law is also explicitly clear: he must step down based on this conflict of interest.”