Early on, Lejeune-Jung had connections with the
German National People's Party (DNVP), for whom he was elected in 1924 as the only Catholic member of the
Reichstag from Middle
Silesia, representing the electoral district of Breslau. In the November election that same year, he was reëlected, and in the years that followed, he was member and chairman of the trade policy board, taking part in the International Parliamentary Conferences in
London (1926),
Rio de Janeiro (1927) and Berlin (1929). An undated written record connected with a memorandum whose author was Lejeune-Jung bears witness to the beginning of the 1920s in Germany. In it, the proposed founding of the Imperial Board of Catholics in the German National People's Party is communicated to the Fulda Bishops' Conference. Lejeune-Jung thereby showed himself to be a representative of the so-called rightwing Catholics, who were monarchists, quite unlike the republican-oriented Catholic
Centre Party. The writers also explicitly distanced themselves from the Centre Party, "which denies the outcome of every force of God, and instead declares the disastrous heresy of the people's sovereignty." The rightwing Catholics did not stand alone with their polemic against the Centre Party. Indeed, even within the Centre Party itself by 1919, a dispute had arisen among Catholics as to Catholics' relationship with the
republican form of government. His political position as a Reichstag member with fundamental conservative convictions notwithstanding, Lejeune-Jung belonged to the moderate forces within the DNVP, who managed to bring themselves to practise positive coöperation in the
Weimar State. Lejeune-Jung belonged to the conservative German Gentlemen's Club (
Deutscher Herrenklub). The petition for a referendum against the
Young Plan (1929), sought by DNVP chairman
Alfred Hugenberg, brought about Lejeune-Jung's – and 11 other members' – departure from the DNVP faction, which meant for him having to give up a secure place on the party list. This secessionist grouping founded on 28 January 1930 the "People's Conservative Union" (
"Volkskonservative Vereinigung"), and also joined themselves on 23 July with the Westarp Group – who themselves had been barred from the DNVP – to form the "Conservative People's Party" (
"Konservative Volkspartei"). The new party, however, did not fare well in the September 1930 election, having only four members returned. Lejeune-Jung, who won no seat, temporarily took up management, but then on 11 June 1932, he joined the Centre Party, with whose right wing he had already had ties even before 1920. Chancellor
Heinrich Brüning had already named Lejeune-Jung as an expert to the German-French Economic Commission in 1931. In the analysis of German-French economic relationships, which Lejeune-Jung undertook in a chronicle under the title "Parisian Impressions, 30 March to 10 April 1930", his skill at precise observation and exact political reasoning became apparent. The core of his supranational concept envisaged coöperation among
European states in the economic domain on the basis of a German-French understanding. Lejeune-Jung floated the idea for a European market in which such sectors as the
potash industry,
heavy industry, the
automobile industry and the electrical industry played a central role. He had not, however, overlooked the
protectionist mindset that
French economic leaders and politicians displayed during discussions about concrete measures, which only bore on a
customs union limited to agricultural products, anyway. ==Resistance activities==