Story highlights Steele concedes information in one memo needed to be verified

Court filing explains for first time why Steele shared his memo

Washington (CNN) The former British spy behind the dossier alleging ties between President Donald Trump's campaign and Russia insists his research was urgent enough to share with top American and British officials, but admits some of his work was not fully verified, according to court documents filed last month in London.

In the new legal filing obtained by CNN, lawyers for former British spy Christopher Steele argue that his investigation into possible collusion between the Trump campaign and Russia, funded by political opponents of Trump, also served a vital national security interest, and that Steele felt obligated to get his work to senior national security officials.

But Steele also concedes that some of the information he passed along to the US and UK governments still "needed to be analyzed and further investigated/verified," according to the court filing. This acknowledgment from Steele referred specifically to one memo he wrote, not his entire dossier.

The filing, first reported by the Washington Times, seeks to defend Steele's involvement in a case against him that claims he failed to do "even the most basic attempt at verification." The defamation case against Steele is playing out in the High Court in London, which is roughly the same as a trial court in the US.

CNN has reported that US investigators have corroborated some aspects of the dossier though not some of the more salacious allegations. The FBI used some materials from the dossier in its successful request for a Foreign Intelligence Surveillance Act (FISA) warrant to conduct surveillance on Trump associate Carter Page.

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