The memo released by the House Intelligence Committee on Friday confirms that the Obama Justice Department and the FBI used an unverified, partisan political screed to obtain a court warrant to spy on the presidential campaign of the opposition party.

The Steele dossier was a compilation of purported intelligence reports authored by former British spy Christopher Steele. Based on anonymous Russian sources peddling fourth-hand hearsay accounts, it alleged a corrupt Trump-Russia conspiracy. It has long been known that the dossier was salacious and unverified, as former FBI director James Comey described it in Senate testimony last June.

The committee’s memo makes clear that, in issuing the FISA warrant authorizing eavesdropping on Trump adviser Carter Page’s telephone, text and email communications, a secret federal court relied heavily on the dossier’s allegations. To justify a FISA warrant, the law requires the Justice Department and the FBI to show probable cause that the target is acting as an agent of a foreign power, in this case Russia; and that the target’s clandestine activities on behalf of that foreign power violate federal criminal law.

The memo explains that former deputy FBI director Andrew McCabe told the committee that without the dossier, the government would not have been able to make that showing.

According to the memo, the court was not told that the dossier was an opposition-research project funded by the Clinton campaign and the Democratic National Committee. Nor was the court informed that Steele told a top Justice Department official he “was desperate that Donald Trump not get elected and was passionate about him not being president.”

And, despite the fact that the original warrant, issued Oct. 21, 2016, was reauthorized three times, the court was never told the FBI’s efforts to verify the document’s sensational allegations were unsuccessful.

Indeed, the memo indicates that the government went to unintentionally absurd lengths to portray the dossier’s claims as corroborated. In one application, the Obama administration argued the allegations were credible because they appeared independently in a Yahoo News report by Michael Isikoff. Unbeknownst to the FBI, however, Isikoff’s source was actually Steele. In effect, the dossier was offered as corroboration of itself.

The FBI was unaware Steele was telling the media the same information he was giving the government because he allegedly lied about his communications with reporters. This finally came to light when Steele gave an interview to left-leaning Mother Jones in which he exposed his status as an FBI informant, prompting the bureau to terminate their relationship.

Last month, two senior Republican senators on the Judiciary Committee sent a criminal referral to the Justice Department, seeking a felony investigation of Steele for making false statements to the FBI. Yet, there is no indication any of Steele’s credibility problems were shared with the FISA court judge who was relying on his information.

The spinning about the memo before and after its publication has been unhelpful. Critics have dismissed it as an effort to malign the FBI and discredit the Mueller investigation. This is wrong. Because so much of the government’s national-security power is exercised in secrecy, it is critical that Congress fulfill its constitutional role of careful oversight — certainly Democrats thought so throughout the 2000s, when they routinely ripped the bureau’s exercise of Patriot Act and surveillance powers.

Moreover, Mueller’s principal mission is to get to the bottom of Russia’s interference with the 2016 election, not to make a criminal case on the farfetched suspicion of Trump campaign collusion in the Kremlin’s anti-American espionage.

Neither, however, has the public been well-served by comparisons of the FISA abuse to Watergate. That scandal was the greatest crisis of the regime in modern American history and involved systematic abuses of government investigative and intelligence agencies.

What the Intelligence Committee memo reveals is not trivial. These are significant derelictions, and they heighten concerns about the degree to which the FBI and Justice Department were enmeshed in the politics of the 2016 election. But before we can draw final conclusions, much more must be known about what other information was presented to the FISA court, and whether valuable intelligence was gleaned in the months of Page’s surveillance.

The memo is a good start. More disclosure, though, is needed.

Twitter: @AndrewCMcCarthy