[3][4] In 1977, on invitation of President J. R. Jayewardene, he switched to the government sector by becoming Director Operations of the Lake House Group of Newspapers.

Thereafter in 1978 he was appointed Permanent Secretary to the Ministry of Agricultural Development and Research and Chairman of the Agricultural Development Authority, Sri Lanka State Plantations Corporation, Land Reform Commission, Pelwatta Sugar Company and Rajarata Food Grain Processing Co.[3] In 1984 Wijeratne was commissioned as lieutenant colonel in the Sri Lanka Army Volunteer Force and became the first commanding officer of the 2nd Battalion, Sri Lanka Rifle Corps on its formation.

[3] Wijeratne resigned from all government posts and his commission when he went into active politics in 1988 when he was appointed Chairman of the United National Party.

[5] He was equally hawkish in dealing with Liberation Tigers of Tamil Eelam (LTTE) and Janatha Vimukthi Peramuna (JVP) militants.

In 2008, Tamil Tigers alleged[12] that Ranjan Wijeratne tried to kill their leader Velupillai Prabhakaran during the 1990 peace process.