The Green Party has elected Derek Wall as its new joint principal speaker, replacing Keith Taylor.
Derek Wall is an economics lecturer and author
Mr Wall, 41, an economics lecturer and author, was elected by 767 votes to 705 for Mr Taylor who had held the post since 2004.
The party has a male and female principal speaker. Sian Berry was elected unopposed in September.
Mr Wall said he had dedicated his adult life to green politics and regarded the role as his greatest challenge yet.
A member of the party since 1980, he said: "Green politics is the politics of survival. Infinite economic growth is impossible on a finite planet.
"We must think deeply about how we transform our economy, our lifestyle and our political institutions."
Mr Taylor, who came third in last year's general election in Brighton Pavilion, with 22% of the vote, said he wished his successor all the best.
The Green Party has 92 Councillors on 38 Councils, two London Assembly members and two MEPs.