 He was elected at the 1945 general election as Member of Parliament (MP) for the Welsh constituency of Llandaff and Barry.His seat was abolished for the 1950 general election, but shortly afterwards the Labour MP for the new Leicester North East constituency became a High Court judge, and Ungoed-Thomas was returned to Parliament in the resulting Leicester North East by-election.Between April 1951 and October 1951, he served as Solicitor General, and received the customary knighthood.