He became a National Party MP in 1960, serving as deputy Prime Minister for a brief period in 1972 and as leader of the opposition from 1973 to 1974 before becoming Premier the following year. He was chairman of the board of governors for the IMF and World Bank (1979–80) and chairman of the ministerial council for the OECD (1982). His term of office was marked by domestic measures to tackle low economic growth and high inflation.