He supported the position of the Independence Party (Selvstendighetspartiet) and was a supporter of Crown Prince Christian Frederik and opponent of the union with Sweden.
Motzfeldt was a member of the Council of State Division in Stockholm 1814–1816, 1818–1819, 1824–1825, 1828–1829, 1831–1832, and 1834–1835, Minister of the Army 1816–1818 and 1819–1822, and Minister of Auditing 1829–1831, 1832–1834, 1835–1836, and 1836–1837.