The infamous dossier that alleges collusion between Donald Trump’s presidential campaign an the Russian government is “probably” credible, the former head of the British Secret Intelligence Service (M16) said Tuesday.

Speaking with BBC’s Newsnight, Sir Richard Dearlove said of the dossier, which was compiled by former M16 officer Christopher Steele, “I think that there is probably some credibility to the content.”

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“I wouldn’t put it any more forcefully than that,” Dearlove added.

The dossier, dismissed by Trump as “fake news,” contains allegations the Kremlin has “been cultivating, supporting and assisting Trump for at least 5 years,” and has sufficient blackmail against the president—including evidence of salacious sexual acts with “a number of prostitutes” in Russia. It also claims members of the Trump campaign had multiple contacts with Russian operatives during the election.

During the presidential transition, former FBI Director James Comey briefed then-president-elect Trump on a two-page synopsis of the dossier. In June, Comey declined to answer questions about the dossier during testimony before the Senate Intelligence Committee, telling members he couldn’t discuss the allegations in an “open setting.” Steele, the author of the memo has said he believes the dossier is 70 to 90 percent accurate.

While U.S. intelligence services work to verify or disprove elements of the Trump dossier, the veracity of it’s claims are playing a pivotal role in Washington D.C. federal court case. BuzzFeed, which published the dossier in January, is fighting a libel suit from a Russian internet entrepreneur named by Steele as one of the people involved in hacking the DNC. As part of its defense, BuzzFeed last month filed a motion to compel the FBI and two other federal agencies to comply with subpoenas regarding the agencies’ verification of the dossier.

Several other new organizations have filed Freedom of Informational Act requests about the dossier.