House Democrats subpoenaed a full, unredacted copy of the special counsel Robert Mueller's final report in the Russia investigation on Wednesday.

Lawmakers are also seeking the underlying evidence for the report.

Attorney General William Barr said in a letter last week that he plans to make a redacted version of the final report available to Congress by mid-April.

But Democratic lawmakers argue that they should get an unredacted copy so they can appropriately conduct oversight of the executive branch. They're also demanding the underlying evidence for the report because they believe it will help them determine whether President Donald Trump committed impeachable offenses, and whether his associates warrant more congressional scrutiny.

One Justice Department veteran criticized House Democrats' move, telling INSIDER, "This subpoena seems to be more political theatre than a serious effort to see the full report."

The House Judiciary Committee voted to authorize a subpoena for a full, unredacted version of the special counsel Robert Mueller's report in the Russia investigation and its underlying evidence on Wednesday.

The vote fell along party lines with all 24 Democrats voting to subpoena the report and all 17 Republicans voting against. But committee chairman Jerry Nadler said he would give Attorney General William Barr some more time to send over an un-redacted copy of the report before moving forward with sending out a subpoena.

The move came after Barr failed to meet the April 2 deadline that House Democrats set for the Justice Department to turn over the documents to Congress.

Barr announced on Friday that he plans to make the final report in the Russia investigation available to Congress and the public by mid-April or sooner.

In a letter to Nadler and Senate Judiciary Committee Chairman Lindsey Graham, Barr said he is working with Mueller to release as much of the report as possible to the public. The attorney general will not send Mueller's report to the White House for a privilege review, a reversal of his earlier statement to Graham on the subject.

The final report is nearly 400 pages long.

Barr said the Justice Department is in the process of redacting the following types of information:

Information that went before a grand jury but did not result in criminal charges

Information that could compromise intelligence sources and methods

Information that could pertain to other ongoing investigative matters

Information that would "unduly infringe on the personal privacy and reputational interests of peripheral third parties."

Read more: House Democrats are preparing for a fierce fight with the Justice Department over some of the most sensitive parts of the Mueller report

Rep. Jerrold Nadler in 2007. Reuters

But Democrats argue that Congress should get an unredacted version of the report, including any grand-jury materials and underlying evidence, so it can appropriately conduct its oversight of the executive branch.

Last month, Barr released a four-page review of Mueller's findings regarding interference in the 2016 election and whether Trump obstructed justice in the investigation.

Barr's review, which listed Mueller's "principal conclusions," said the special counsel did not find sufficient evidence to bring a criminal charge of conspiracy against Trump, the campaign, or anyone associated with it.

Barr's letter also said that while Mueller did not "draw a conclusion — one way or the other — as to whether the examined conduct constitutes obstruction," Mueller's report "also does not exonerate" Trump of any criminal wrongdoing.

But Barr, in consultation with Deputy Attorney General Rod Rosenstein, decided that the special counsel's findings were "not sufficient" to determine that Trump committed obstruction of justice.

Read more: Barr says he will not send Mueller's report to the White House before the public and that he plans to release it by mid-April

Attorney General William Barr. AP Photo/Andrew Harnik

Their conclusion sparked immediate calls for the full report to be made public, and Democratic lawmakers accused the attorney general of bias, pointing to a memo he wrote last year calling the obstruction probe a "legally insupportable" inquiry that should not be sanctioned by the Justice Department.

House Democrats' move to subpoena the full report marks yet another escalation in the brewing fight between lawmakers and the Justice Department over Mueller's findings. Because of the unprecedented nature of the conflict, experts say it's likely a court will have to intervene.

Meanwhile, the Reporters Committee for Freedom of the Press (RCFP) signaled its backing of congressional Democrats when it filed a request this week asking a federal court to authorize the release of any grand-jury material "cited, quoted, or referenced" in Mueller's final report.

Read more: Prosecutors left a trail of breadcrumbs about Trump's finances, and House Democrats are now digging deeper

Patrick Cotter, a longtime former federal prosecutor who worked with members of Mueller's team, told INSIDER, "A subpoena from Congress is not an exception" to the Federal Rule of Criminal Procedure 6(e), which is the statute that governs the release of grand-jury information. "Therefore, since I assume someone in Congress has read the law, this subpoena seems to be more political theatre than a serious effort to see the full report."

Cotter also noted Barr's pledge to disclose as much information as he can from Mueller's report — especially given the intense public interest in the special counsel's findings — within the next few weeks.

"That does not seem in any way unreasonable given the reported size of the Mueller report," Cotter said. "Therefore, the action by Congress seems unreasonably premature at best, and an undignified political act that will only accentuate their impotence, at worst."