[3] Kirwan first stood for the House of Representatives at the 1966 federal election, opposing the incumbent Liberal MP Gordon Freeth.

He reprised his candidacy at the 1969 election and unexpectedly defeated Freeth, by then an incumbent cabinet minister in the Gorton government.

[1] Freeth's defeat was attributed to remarks he had made as external affairs minister which were seen as not sufficiently anti-communist, causing the Democratic Labor Party to direct its preferences to Kirwan, and to an economic recession in his electorate.

[5] Kirwan was defeated after a single term at the 1972 election, with Peter Drummond reclaiming Forrest for the Liberal Party despite the ALP's overall victory.

[6] Kirwan unsuccessfully stood for the Western Australian Legislative Assembly at the 1973 Bunbury state by-election, losing to Liberal candidate John Sibson.