Carter Page, a former foreign policy adviser of U.S. President-elect Donald Trump, speaks at a news conference at RIA Novosti news agency in Moscow, Russia, Monday, Dec. 12, 2016. AP Photo/Pavel Golovkin The FBI used information from the explosive, unverified dossier detailing President Donald Trump's alleged ties to Russia to obtain a warrant to secretly monitor former Trump adviser Carter Page.

That same dossier — a collection of memos compiled by former British intelligence agent Christopher Steele — has been used in other elements of the US investigation into whether there was any inappropriate contact between Trump campaign associates and Russia.

CNN first reported the FBI's use of the dossier to secure the Foreign Intelligence Surveillance Act (FISA) warrant on Page, the former Trump foreign-policy adviser who has appeared to be at the center of the Trump-Russia investigations — due in part to his previous work in Russia and his communications with Russian officials.

President Donald Trump has previously called the dossier "phony stuff" and "fake news."

Page has resurfaced in headlines at several points since the 2016 election — most recently last week, when he declared that he could not "definitively" say that he never discussed US sanctions with any Russian official. The dossier alleges Page met senior Russian officials during a trip to Moscow last July, when he gave a speech critical of US policy toward Russia. It also alleges Page discussed sanctions and business opportunities with the Russian officials. Page has denied the information contained in the dossier.

Page has repeatedly denied any wrongdoing and said suggestions of his alleged involvement in any perceived collusion between the Trump camp and Russia were "lies."

Page said in a statement to Business Insider on Tuesday: "I look forward to the Privacy Act of 1974 lawsuit that I plan to file in response to the civil rights violations by Obama Administration appointees last year."

"The discovery process will be of great value to the United States, as our nation hears testimony from them under oath and we receive disclosure of the documents which show what exactly was done in 2016."

The matter of those sanctions felled another Trump adviser in recent months. Former national security adviser Michael Flynn resigned from Trump's White House in February amid questions about his conversations with Russian ambassador Sergey Kislyak.

Natasha Bertrand contributed reporting.