Democrats said Friday that congressional Republicans are guilty of obstruction of justice after the House intelligence committee released a GOP-authored memo arguing the FBI used tainted anti-Trump sources to justify spying on a Trump campaign figure.

Top Democrats also warned President Trump against using the memo as justification for firing special counsel Robert Mueller or Deputy Attorney General Rod Rosenstein — who was implicated in the alleged abuses detailed in the new memo.

Democrats said they believe the memo’s release was intended to undercut Mr. Mueller’s probe into Russian meddling in the 2016 election. Mr. Rosenstein ordered that probe after Mr. Trump fired FBI Director James B. Comey, who was involved in spreading the tainted information detailed in the new GOP memo.

“This Republican campaign is a betrayal of the American people,” said Rep. Jerrold Nadler and fellow Democrats on the House Judiciary Committee.

Added Sen. Mark Warner, the top Democrat on the Senate intelligence committee: “The release of this memo by House Intelligence Committee Republicans and the White House, over the objections of the FBI and the Department of Justice, is reckless and demonstrates an astonishing disregard for the truth.”

Mr. Warner and Mr. Nadler were part of a group of 10 Democrats who wrote a letter telling Mr. Trump the new memo should not be the basis for any more firings of Justice Department figures.

“We write to inform you that we would consider such an unwarranted action as an attempt to obstruct justice in the Russia investigation. Firing Rod Rosenstein, DOJ Leadership, or Bob Mueller could result in a constitutional crisis of the kind not seen since the Saturday Night Massacre,” the Democrats said.

The memo in question was written by Rep. Devin Nunes, chairman of the House intelligence committee, who has access to the source materials and wrote a four-page document arguing the FBI used tainted materials to obtain a secret court warrant to surveil Carter Page, a Trump campaign figure.

Mr. Nunes says not only was the original FBI information tainted by bias, but the FBI and Justice Department didn’t disclose that bias or other factors to the secret court that approved the warrant.

Mr. Comey and Mr. Rosenstein were both involved in signing off on the deficient applications to the court, Mr. Nunes says.

Mr. Trump agreed to declassify the memo on Friday, leading to its release.

But Mr. Warner said the underlying source materials don’t back up Mr. Nunes’ conclusions. He didn’t say what specifically was inaccurate.

The memo puts some Democrats in the awkward position of defending the Foreign Intelligence Surveillance Act — the law used to get the secret court warrant allowing spying — that they’ve long criticized. Those Democrats have said Americans’ rights could be trampled by the FISA.

Mr. Nunes’ memo argues that’s what happened in this case — leaving Democrats to defend the law they have questioned.

Sen. Patrick Leahy, Vermont Democrat and prominent FISA critic, said his complaints about the GOP decision to release the memo have “absolutely nothing to do with what is wrong with FISA.”

“The memo deliberately omits key facts and intentionally distorts the multilayered process led by rank and file national security professionals that is required to obtain and renew a judicial warrant for a suspected foreign agent,” Mr. Leahy said. “In this case that meticulous process led to a warrant for Trump campaign advisor Carter Page, an individual targeted for recruitment by known Russian spies even before he joined the president’s team.”

Mr. Nunes, though, cites former FBI Deputy Director Andrew McCabe — who abruptly sped up his retirement this week — as telling the intelligence committee the FISA warrant wouldn’t have been obtained without the tainted information.

That tainted information came from the so-called Steele Dossier, a document funded by the Democratic National Committee and the Clinton campaign, which the FBI has said is unverified and salacious.

Sen. Cory Booker, New Jersey Democrat, said the Nunes memo’s release amounted to “treasonous” behavior.

Mr. Booker said Congress should pass legislation specifically protecting Mr. Mueller from being fired amid the probe.

“President Trump and his allies in Congress are stopping at nothing to interfere with the special counsel’s Russia probe, even if it means putting the safety of the American public at risk, and degrading the rule of law,” he said.

• Seth McLaughlin contributed to this article.

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