As a founding member, Karunaratne was associated with the
Sri Lanka Freedom Party (SLFP) earlier in his career. He was elected chairman of the
Rambukkana town council in 1953 at the inauguration of that local body. He played a crucial role in Prime Minister
S. W. R. D. Bandaranaike's victory in the 1956 General Election by addressing a number of meetings, appealing to his relations and party supporters to rally behind the victory. Karunaratne entered the legislature in 1958 when S. W. R. D. Bandaranaike appointed him to the House of Representatives. 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. At the general election of March & July 1960, he contested the newly demarcated
Rambukkana seat as the candidate of the SLFP and was elected by a majority of over 6000 votes. 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. In 1963, over a difference of opinion, Karunaratne resigned from the SLFP and joined the
United National Party (UNP) and helped
C. P. de Silva initiate the
Sri Lanka Freedom Socialist Party, which was in coalition with the UNP. He was appointed Minister of Social Services in the
Dudley Senanayake government. Though he was defeated at the General Election of 1970, he recontested the
Rambukkana electorate as the candidate of the UNP in July 1977 and was elected by a comfortable majority and reappointed as Minister of Social Services by Prime Minister
J. R. Jayewardene. In 1982 he led the Sri Lankan delegation to the World Assembly on Aging held in Vienna which was sponsored by the United Nations. Thereafter he made a tour of Denmark, Sweden, Thailand, Singapore, India, and Japan. 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. ==Contribution to Society==