As the President's Secretary he was the top civil servant in the country and de facto head of the Sri Lanka Administrative Service.

He had also been Chief Technical Advisor/Vocational Training Specialist in the Regional Office of the International Labour Organization (ILO) for Asia & Pacific, Thailand and had worked as a Consultant of the United Nations Development Programme for the Government of Maldives.

He is also the current Chair of the Information and Communication Technology (ICT) Committee of ESCAP – the Economic & Social Commission for Asia and the Pacific.

In September 2010, Weeratunga was unanimously elected as the Chairman of the Commonwealth Telecommunications Organisation at its 50th Council Meeting.

Weeratunga with Anusha Pelpita was acquitted from a case charging them with misappropriation of Government funds by distributing ‘Sil’ cloth to temples island-wide at a cost of Rs.