[citation needed] Macklin was the founding member of the Australian Democrats in Queensland and led the party in that state from 1977 to 1980, when he was elected to the Senate.

[3] From 24 March to 30 June 1990, he served as interim parliamentary leader after the resignation of Haines from the Senate to contest a House of Representatives seat.

[4] He served on eleven parliamentary committees, including those having oversight of the National Crime Authority and the Australian Security Intelligence Organisation.

As Director of Development for the University of Queensland, he was responsible for putting fundraising on a professional basis with an annual appeal and bequest programs.

[citation needed] In 1994, he was appointed inaugural CEO of Hall Chadwick Education Advisory, a specialist consultancy within a large chartered-accountancy practice and was responsible for establishing benchmarking of private school finances in Australia in conjunction with the peak body.