General Haller condemned Piłsudski's May Coup d'État which resulted in him being retired on 31 January 1926. In the 1920s along with his wife Alexandra and his son Eryk he settled in Pomerania in the Gorzuchowo mansion, near Chełmno. During the years 1936-39, he was one of the organizers and leaders of Front Morges which was in opposition to the government of the sanacja regime. On 10 October 1937, on the Labor Party's Constitutional Congress he was elected the head of the party's Principal Board.