Prüm was born in Troisvierges, in the far north of the Grand Duchy, on 9 July 1886. His father, Émile Prüm, was a fervent Roman Catholic and a prominent conservative politician, and this greatly affected his political outlook. He and his brother Emmanuel were sent to university at Leuven, where he joined K.A.V. Lovania Leuven, a Catholic fraternity. While his brother became a priest, Pierre trained as a lawyer. Like his father, he sought political office, and entered politics himself, representing the canton of Clervaux in the Chamber of Deputies. As a conservative, he joined the Party of the Right when it was founded, in 1914. However, Prüm left the Party of the Right in 1918 to form his own party, the Independent National Party.
Government
In 1925, the PNI seized upon the inability of the PD government to pass railway reforms. In the legislative elections of 1 March, the ruling Party of the Right lost its majority in the Chamber of Deputies, winning only 22 of the 47 seats. Unwilling to form a coalition with any parties that had blocked its railway reforms, Prüm was invited to form a government, provided that he could form a majority coalition. Taking in an eclectic collection of Radical Socialists and dissident conservatives, with the additional informal backing of the Socialist Party, Prüm's government took office on 20 March. Prüm sought to improve relations with France and Germany, which had been alienated by the formation of the Belgium-Luxembourg Economic Union in 1921. On 9 October, Prüm negotiated a working arrangement on the co-ordination of iron production in France and Luxembourg. At the same time, the Locarno Treaties were signed between seven European states ; the treaties confirmed the inviolability of the borders redrawn by the Treaty of Versailles. These two arrangements would go a considerable distance towards calming the tensions over Luxembourg that had flared up during and after the First World War. When the government turned its attention back to domestic affairs, it did not fare so well. The Socialist Party had supported Prüm throughout 1925, despite not being rewarded with a cabinet position. As a mark of its debt to the Socialists, in May 1926, the government sought to introduce a bill improving working conditions. The Liberals, who predominantly represented employers and the professional class, were angered, and withdrew their support for the government. Without a majority, Prüm tendered his resignation to Grand Duchess Charlotte on 22 June.