While practising as a barrister, Millhouse entered the South Australian House of Assembly on 7 May 1955 as the Liberal and Country League member for Mitcham, a safe LCL seat in southeastern Adelaide. Millhouse rapidly gained a reputation as both the intellectual driving force behind the LCL and an outspoken spokesperson for the urban middle class faction of the LCL, a group under-represented within the party hierarchy. Millhouse ran for the LCL leadership pre-selection following leader Sir Thomas Playford's retirement, but lost to Steele Hall, another member of the LCL's progressive faction. Instead, following the LCL's return to power at the 1968 election, Millhouse was given the portfolios of Attorney-General, Aboriginal Affairs, Social Welfare, and Labour and Industry. In these roles, Millhouse gained a reputation as a crusader for progressive social change as he sought to position South Australia as a national leader on social issues. During 1969 Millhouse was the architect and the major proponent for abortion on health grounds in South Australia, a decision he would come to regret decades later, claiming it had become "abortion on demand". In the wake of the LCL's 1970 election loss, Millhouse was elected Deputy Leader of the Opposition on 2 June. After the LCL also lost the 1973 state election, Millhouse resigned from the party on 18 March 1973 to form the Liberal Movement, along with former premier Steele Hall and a number of other senior LCL members, following growing dissatisfaction at the continuing conservatism of the LCL. He led the Liberal Movement at the 1975 state election, where the party received 18% of the vote, though only winning four seats. In 1976, all Liberal Movement parliamentary members except for Millhouse returned to what by then had become the South Australia branch of the Liberal Party. Millhouse chose instead to form a new political party, named the New LM; before merging that with the Australia Party, the Centre-Line Party and other like minded groups to form the Australian Democrats. As a sitting member, he became the first Australian Democrats Member of Parliament in 1977. As a Democrat, Millhouse retained his seat of Mitcham at the 1977 and 1979 state elections. He continued to campaign for progressive social issues, including the introduction of a bill to legalise prostitution in South Australia.
At his retirement sitting, he announced his appointment as Chief Justice of the High Court of Kiribati, a position he held until January 2011. He was Chief Justice of Nauru from 3 April 2006 to late 2010. Following his retirement as Chief Justice of Kiribati, he served as a judge of High Court of Tuvalu from February 2014 and March 2015.
Personal life
He married Ann in 1957 and had three daughters and two sons. Millhouse died on 28 April 2017, aged 87. Sir Eric Millhouse, lawyer and champion of returned soldiers, was an uncle.
