On 14 November 1881 Léon Gambetta, President of the Council and Minister of Foreign Affairs, named Deloncle Chief of Staff to Eugène Spuller, Under-Secretary of State. In January 1881 Gambetta made him Consul 1st Class. During this period Deloncle was given several diplomatic missions as consul general. Deloncle published many accounts of his journeys and missions, notably that to Burma. He was in turn Secretary of the Société de géographie and the Société des etudes maritimes at coloniales, and was founder of many philanthropic societies including the Association pour la défense des droits individuels. Deloncle was sent on an official mission to India by Jules Ferry in 1883. His dispatches were embellished and enlivened by Octave Mirbeau and published under the pseudonym "Nirvana" in 11 instalments in "Le Gaulois" between 22 February and 22 April 1885. They take the form of 11 letters written by a traveller who visits Aden, Ceylon, the French colony of Pondicherry, Peshawar and Darjeeling. It is a work of propaganda, in which the anonymous author contrasts the brutal oppression of British colonialism with the civilized tolerance of the French. On 10 July 1885 Deloncle was attached to the residence general at Huế and given charge of commercial negotiations with China. On 7 August 1885, when he was about to leave for China, he was instead appointed consul in Melbourne. He asked for a postponement due to his forthcoming marriage. On 7 September 1885 he married Léonie Claire Donnat in Paris. They divorced on 14 December 1904. On 26 December 1885 he turned down the offer of the position of Consul at Melbourne. On 22 September 1889 Deloncle ran as Opportunist Republican candidate for the Castellane constituency of Basses-Alpes, and was elected in the first round by 2,391 votes out of 4,265. He sat with the democratic left group, and was a member of the committees on Customs and Review of Administrative Services. He specialized in foreign, colonial and customs issues, and was very active in the chamber. In 1890 he became director of the journal "Le Siècle", where he mainly published articles on foreign policy issues. In the Chamber he was involved in discussion on improving trade relations between France and Greece and the Paris Universal Exposition of 1900. In 1892 Deloncle instigated construction of the Great Paris Exhibition Telescope of 1900, the largest refracting telescope ever constructed, as the centerpiece of the Paris Universal Exposition of 1900.