He was elected a member of the Reichstag, where he joined the National Liberal party, for like many other exiles be was willing to accept the results of Otto von Bismarck’s work. In 1868 he published a short life of Bismarck in French, with the object of producing a better understanding of German affairs, and in 1870, owing to his intimate acquaintance with France and with finance, he was summoned by Bismarck to Versailles to help in the discussion of terms of peace. In the German Reichstag he was the leading authority on matters of finance and economics, as well as a clear and persuasive speaker, and it was chiefly owing to him that a gold currency was adopted and that the German Imperial Bank took form; in his later years he wrote and spoke strongly against bimetallism. He was the leader of the free traders, and after 1878 refused to follow Bismarck in his new policy of protection, state socialism and colonial development.
In 1892 he retired from political life and died in 1899. Bamberger was a clear and attractive writer and was a frequent contributor on political and economic questions to the Nation and other periodicals. His most important works are those on the currency, on the French war-indemnity, his criticism of socialism and his apology for the Secession.