In the
1955 election, Killen was elected to the
House of Representatives for the Brisbane seat of
Moreton, holding the seat until 1983. In the
1961 election, Killen narrowly retained his seat, and since
Robert Menzies' Liberal government was re-elected with a majority of only two, and with Killen's seat the last to be declared, it was claimed by some that Killen had 'saved' Menzies and his government. Killen claimed that Menzies had phoned him, saying "Killen, you are magnificent!", and that story was widely repeated for many years, but he later confessed he had made it up for the
Courier-Mail to overcome his disappointment at not, in fact, receiving such a call from Menzies. By the late 1960s Killen had somewhat moderated his views, and in the government of
John Gorton he served as
Minister for the Navy from 1969 to 1971. When
William McMahon became Prime Minister, Killen was dropped from the Ministry. After the Liberals lost office to
Labor under
Gough Whitlam, he served in the
Shadow Cabinet under
Billy Snedden and
Malcolm Fraser from 1972 to 1975, acting as the party spokesman on Education and later Defence. He served as
Minister for Defence in the Fraser Government from 1975 to 1982. During this time he oversaw a major review of the
Australian Defence Force and also the military build-up which followed the
Soviet invasion of
Afghanistan in 1979. He oversaw the largest single piece of Defence expenditure in Australian history, the purchase of 75
F/A-18 Hornets. Killen was moved out of Defence in a 1982 reshuffle. He was made a
Knight Commander of the Order of St Michael and St George, becoming "Sir James Killen KCMG", and appointed
Vice-President of the Executive Council, a position he held until the defeat of the Fraser government in
1983 election by Labor under
Bob Hawke. He became
Father of the House of Representatives in April 1983, and resigned his seat of Moreton in August 1983 (the first Queensland Member of the House of Representatives to resign), and returned to his legal practice. He was a prominent figure at the Brisbane bar through the 1980s and 1990s. Killen was a prominent
monarchist and was elected to the
Constitutional Convention in 1998 as an opponent of an
Australian republic. In 2004, he was made a
Companion of the Order of Australia (AC). Killen had a reputation as a great parliamentary wit who developed close friendships with many people on both sides of politics, among them
Gough Whitlam,
Fred Daly and
Barry Cohen. He wrote the preface to Daly's collection of political anecdotes,
The Politician Who Laughed (1982). ==Private life==