His father was Andrew Dissanayake, who served as a Member of Parliament and the Parliamentary Secretary to the Minister of Nationalised Services and Shipping in the Sri Lanka Freedom Party government of S.W.R.D.

He thereafter started his legal practice in the unofficial bar in the Colombo District Court as a junior to B. J. Fernando, PC.

[1][2] Following is father's legacy, he sought nomination from the Sri Lanka Freedom Party for the 1970 general elections from the Nuwara Eliya electorate, but was refused.

That year a modification of the law by Minister of Justice, Felix Dias Bandaranaike to benefit Nanda Ellawala, allowed for Dissanayake to retain his civic rights and contest the by-election regaining his seat in parliament in 1972.

[2] He comfortably secured his Nuwaraeliya-Maskeliya multielectorate seat in the 1977 general elections and was appointed as the minister of Mahaweli Development.

In the same year Dissanayaka joined Lalith Athulathmudali to form United National Democratic Front (DUNF) which was a rising political force of that era.

Later he rejoined UNP and was appointed to the parliament as a national list MP and was offered a vital portfolio in the Wijethunga Government.

In a contest held among UNP MPs to choose the opposition leader Dissanayaka recorded a comfortable victory over previous prime minister Ranil Wickramasinghe.

HIs presidential ambition was cut short when he was assassinated by a female suicide bomber of the Liberation Tigers of Tamil Eelam (LTTE) while he was addressing an election meeting at Thotalanga.

[6] His wife Srima Dissanayake ran in his stead, but was defeated by People's Alliance candidate and Prime Minister Chandrika Kumaratunga.