Ratnayaka was born to a political family from Deniyaya, where his uncle Victor Ratnayake, MBE was a notable legislator. He was educated at the Royal College Colombo, where he became the Head Prefect. He proceeded to study in the United States and graduated from Lewis & Clark College with a bachelor's degree in business administration studies in 1993.[1]
He entered politics in 1999, having been elected as a member of the Southern Provincial Council. In 2000, he was elected to parliament from the Matara District. He served as Deputy Minister of Power and Energy from 2002 to 2004. Having been re-elected in 2010 and 2015. From January 2015 to September 2015 he served as the chief of staff to the prime minister until he was elected to parliament in 2015 and appointed as a Cabinet minister of Law and Order in the Good Governance Government.[2][3] He served as a Cabinet minister till 2019 when he resigned from his portfolio, serving as an opposition member of parliament till 2020. In July 2022, he was appointed by President Ranil Wickremesinghe as his chief of staff and senior adviser to the president on national security.[4]
