From 1990 to 1993, Warren held the position of Special Assistant to the Rt. Hon. Jean Chrétien, leader of the Liberal Party of Canada. In addition, from 1993 to 1996, Warren served as Chief of Staff in a number of federal ministries.
In 2003, 2007, and 2011 he was Chairman of the War Room in the successful Ontario Liberal Party election campaigns; federally, he managed the Liberal Party of Canada’s War Rooms in 1993 and 2000. In 2020, he worked in several states on the victorious Biden-Harris campaign.
Warren is an award-winning author and journalist and has assisted clients on a wide variety of communications, strategic and regulatory matters. His legal practice focuses on administrative, Indigenous and governmental affairs.
Warren is a former member of the executive of the Ontario Bar Association and has sat on the communications committee of the Canadian Bar Association. He has been an adjunct professor at the University of Calgary’s Faculty of Law and an instructor in law at Carleton’s School of Journalism.
Warren has been a columnist with the Ottawa Citizen, National Post, Hill Times and nationally with the Postmedia media chain, and published his best-seller, The War Room: Political Strategies for Business, NGOs, and Anyone Who Wants To Win, in 2007. His third book in the X series, Age of Unreason, was released in December 2019. This is his tenth book and a follow up to 2017’s bestselling Recipe for Hate and 2018’s New Dark Ages.
In 2025, Penguin Random House is globally publishing his newest book, The Hidden Hand. It is about the worldwide propaganda campaign against Israel and the West.