The British government was given details last December of allegations made by former intelligence officer Christopher Steele that there were contacts between Donald Trump's presidential campaign and Moscow, according to court papers.
Mr Steele was behind a dossier that emerged in January alleging the links, which Mr Trump's campaign denied.
Mr Steele and his company are currently defending a defamation case in the High Court in London brought by a Russian venture capitalist named in the dossier.
According to documents in the case Mr Steele in December handed a memo to a “senior UK government national security official acting in his official capacity on a confidential basis in hard copy form”.
He passed on the information because it was of "considerable importance in relation to alleged Russian interference in the US presidential election," the court filing said.
It said the information had "implications for the national security of the US and the UK,” and "needed to be analysed and further investigated/verified".
Former British intelligence officials have said Mr Steele spent years under diplomatic cover working for MI6 in Russia and Paris. He later supplied the FBI) with information on corruption at FIFA, international football’s governing body. .