Nicknamed "Serbian Bob" or the "member for Belgrade" as a result of his pro-Serb views, he was one of the few Labour MPs to vote against the NATO intervention over Kosovo in 1999. Wareing was a member of the Socialist Campaign Group, and frequently rebelled against the government. On 31 October 2006, Wareing was one of 12 Labour MPs to back Plaid Cymru and the Scottish National Party's call for an inquiry into the Iraq War.