Having unsuccessfully fought Wimbledon in the 1955 General Election, Janner represented Leicester North West from the 1970 general election until February 1974, succeeding his father, Sir Barnett Janner, a former Chairman of the Zionist Federation of Great Britain. His father announced his retirement from the Commons two days before candidate nominations closed in 1970, and his son was quickly chosen in his place. Posters imploring electors to "Vote Janner" had already been printed, and thus did not need to be scrapped.