ISRAEL:
Rabbi David Golinkin (Masorti) of Jerusalem has ruled that "it is permitted (and perhaps even obligatory) to eliminate" the custom of not eating kitniyot during Pesach in Israel. See Rabbi Golinkin's complete teshuva in Hebrew or an English summary.
Machon Shilo has ruled that all Jews in Israel may consume kitniyot during Pesach. See the complete teshuva in Hebrew or an English summary. The signatories to this ruling were Rav David Bar-Hayim, Rav Yehoshua Buch, and Rav Chaim Wasserman, all of Jerusalem.
USA:
Rabbi Shammai Engelmayer (Conservative) of
In 2005, Rabbi Jeffrey Wohlberg (Conservative) then Senior Rabbi of Congregation Adas
In 2010, following Rabbi Wohlberg's lead, Rabbi Seymour Rosenbloom of Congregation Adath Jeshurun, Elkins Park, PA stated in his congregation's Passover Guide “it is permissible to use these products (kitniot) on Passover, although one may elect to continue to refrain from them out of respect for ancestral tradition."
See also an Orthodox discussion of the prohibition of kitniyot.