His nomination needs to be confirmed at a party congress next month. The Union of Rightist Forces is associated with the economic reformists of the immediate post-Soviet era.
Speaking at an antigovernment demonstration in central Moscow today, Nemtsov said he is for a "Russia without lawlessness."
"We absolutely disagree with both [President Vladimir] Putin's plan and his course. As both the plan and the course are the way to the third world," Nemtsov said.
President Vladimir Putin is due to stand down after the March 2008 election. Putin is, however, leading the candidate list of the pro-Kremlin Unified Russia party in the December 2 parliamentary elections, a move likely to secure his influence over Russian politics.