After passing with merits in his Cambridge Senior Exam, World War II erupted, hindering his future plans of attending university in England.

He has the unique distinction of being the first Sinhalese to enter parliament as an appointment member, a tribute to the silent but very effective and unrepresented Sinhala opinion and interests at the time.

He retained the same seat in the subsequent General Election held in July 1960 and was appointed Parliamentary Secretary to the Minister of Justice by Premier Sirimavo Bandaranaike.

He strengthened the relations between Sri Lanka and ESCAP, UNICEF, and ICSW and also signed several agreements with foreign organisations and governments beneficial to children, the handicapped, and elders.

During his stewardship as Minister of Social Services, Karunaratne initiated action to enhance public assistance and introduced rehabilitation programmes for the handicapped.