(CNN) Rudy Giuliani is working with foreign clients as he continues to advise President Donald Trump on the Russia investigation, which raises conflict of interest and federal ethics issues, according to a new report.

Giuliani told The Washington Post in interviews that he maintains clients in Ukraine, Brazil and Colombia, as well as delivers paid speeches for Mujahedin-e-Khalq , a controversial Iranian exile organization that was formerly listed as a terrorist group by the US State Department.

Lobbying experts told the Post that some of Giuliani's work for foreign clients is likely to require disclosure under the Foreign Agent Registration Act.

According to the Post, Giuliani has not registered with the Department of Justice for his work, arguing that it's not necessary because Trump isn't paying him for his counsel and he does not directly lobby the US government.

"I don't represent foreign governments in front of the US government. I've never registered to lobby," he told the Post.

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