Ponnambalam was re-elected at the 1956 parliamentary election but lost his seat at the March 1960 parliamentary election. He tried unsuccessfully to re-gain his seat at the July 1960 parliamentary election. He was elected at the 1965 parliamentary election. After the election the ACTC joined the UNP led national government and Ponnambalam was offered a ministerial position which he declined. Between 1967 and 1969 Ponnambalam led Ceylon's delegation to UN General Assembly. Ponnambalam lost his seat again at the 1970 parliamentary election.