Mr Humphries, who served in the Senate for 10 years before being rolled by current Liberal senator Zed Seselja in a bitter coup, has been a deputy president of the Tribunal since 2015.

While Mr Humphries has made a number of newsworthy decisions in his time at the Tribunal, the decision to step away from the role is believed to be uncontroversial, allowing him to focus on other projects.

Among the first members to be elected to the ACT's Legislative Assembly in 1989, Mr Humphries is working on a doctoral thesis on the history of self-government in the territory.

Appointments to the Administrative Appeals Tribunal under the Liberal government have drawn controversy with a high number of former Liberal politicians or staffers handed positions.

However Mr Humphries had resigned from the party before his appointment, after criticising the party for "creeping conservativism". He also has legal qualifications, working as a solicitor before entering politics.

The Administrative Appeals Tribunal confirmed Mr Humphries would be stepping down either at the end of the year or early next year.