After legal training he joined the Prussian government service and became a judge. Lasker was a deputy in the Prussian diet from 1865 to 1879 and in the Reichstag of the North German Confederation and then of the German Empire from 1867 to 1883. He took the lead in the formation of the National Liberal Party in 1866 and supported Bismarck's unification of Germany. He was most active in working out the unification of the legal administration and procedure of the empire (1877) and of its economic structure.

An opponent of Bismarck's exploitation of parliamentarianism and a convinced adherent of the tenets of free trade, Lasker broke with the National Liberal Party after quarrels over constitutional reform and the introduction of a protective tariff in 1878. This “secession” was followed in 1884 by the fusion of Lasker's followers with the German Progressive Party to form the German Radical Party. He died while on a visit to the United States.