At the 2016 federal election, in the 150-seat House of Representatives, the incumbent Coalition government was reelected with 76 seats, a majority of one seat. The Labor opposition won 69 seats. Five other MPs were elected to the crossbench, with the Greens, the Nick Xenophon Team, Katter's Australian Party, and independents Andrew Wilkie and Cathy McGowan winning a seat each.
According to the 1−100 Gallagher Index, the disproportionality in the lower house is comparatively high at about 12.7 in 2016 − compared to 9.7 in 2013, 11.3 in 2010 and 10.3 in 2007.
House of Representatives (IRV) — Turnout 91.01% (CV) — Informal 5.05%[2]
In the time elapsed between the 2016 election and the following federal election, many parliamentarians resigned from their seats, while some were disqualified by the High Court of Australia. The parliamentary eligibility crisis involving dual citizenship was responsible for a significant portion of these departures, although the cases of Barnaby Joyce and John Alexander only left brief vacancies due to their prompt returns in by-elections. Some individual parliamentarians also made an impact by changing their party membership or independent status.
5 April 2017: The High Court finds that Bob Day was not eligible to be elected under Section 44(v) of the Constitution due to holding a pecuniary interest in an agreement with the Commonwealth.[7]
19 April 2017: Family First Senator Lucy Gichuhi declared elected as a Senator for South Australia by the High Court on a countback to replace Day.[8]
14 July 2017: Greens Senator and co-deputy leader Scott Ludlam resigns after discovering that he still held New Zealand citizenship, making him ineligible to sit in parliament due to Section 44(i) of the Constitution.[10]
18 July 2017: Greens Senator and co-deputy leader Larissa Waters resigns after discovering that she held Canadian citizenship by birth, making her ineligible to sit in parliament due to Section 44(i) of the Constitution.[11]
16 August 2017: Liberal Slade Brockman is appointed as a Senator for Western Australia to replace Back, being sworn in the next day.[12]
27 October 2017: The High Court finds that Greens Senator Scott Ludlam of Western Australia, Greens Senator Larissa Waters of Queensland, One Nation Senator Malcolm Roberts of Queensland, Nationals Senator and deputy leader of the National Party Fiona Nash of New South Wales, and Deputy Prime Minister and leader of the National Party Barnaby Joyce (the member for New England) were all ineligible to be elected to and sit in Parliament under Section 44(i) of the Constitution, due to all holding foreign citizenship.[13]
2 November 2017: President of the Senate and Liberal Senator Stephen Parry of Tasmania resigns after discovering he held British citizenship by descent, making him ineligible to sit in parliament due to Section 44(i) of the Constitution.[15]
10 November 2017: Greens Senator Jordon Steele-John of Western Australia, Greens Senator Andrew Bartlett of Queensland, and One Nation Senator Fraser Anning of Queensland are declared elected as Senators by the High Court, to replace Ludlam, Waters, and Roberts (respectively).[16]
13 November 2017: Liberal MP John Alexander, the member for Bennelong, resigns after discovering he held British citizenship by descent, making him ineligible to sit in parliament due to Section 44(i) of the Constitution.[17]
13 November 2017: Greens Senator Jordon Steele-John of Western Australia, Greens Senator Andrew Bartlett of Queensland, and One Nation Senator Fraser Anning of Queensland (who immediately resigned from the party to sit as an independent) are sworn in as senators to replace Ludlam, Waters, and Roberts (respectively).[18]
14 November 2017: Jacqui Lambie Network Senator Jacqui Lambie resigns after discovering that she held British citizenship by descent, making her ineligible to sit in parliament due to Section 44(i) of the Constitution.[19]
14 November 2017: Rex Patrick of the Nick Xenophon Team is appointed as a Senator for South Australia to replace Nick Xenophon,[20] being sworn in the next day.[21]
22 November 2017: Nick Xenophon Team Senator Skye Kakoschke-Moore resigns after discovering that she held British citizenship by descent, making her ineligible to sit in parliament due to Section 44(i) of the Constitution.[22]
2 December 2017: 2017 New England by-election held. Former Deputy Prime Minister and Leader of the Nationals, Barnaby Joyce, was returned to his former seat after renouncing his New Zealand citizenship.
16 December 2017: 2017 Bennelong by-election held. Previous Liberal MP for Bennelong John Alexander was returned after renouncing his British citizenship.
22 December 2017: The High Court declares Liberal Jim Molan elected as a Senator for New South Wales, taking the seat formerly held by Fiona Nash.[23]
25 January 2018: Labor Senator Sam Dastyari of New South Wales resigns due to being the subject of a Chinese-related donations scandal.[24]
1 February 2018: Labor MP David Feeney announces his resignation from politics, due to dual citizenship concerns, which takes effect immediately.[25]
9 May 2018: The High Court rules that ACT Labor Senator Katy Gallagher is ineligible to be elected to and sit in Parliament under Section 44(i) of the Constitution, due to not renouncing British citizenship in time. Following the ruling, Labor MPs Josh Wilson, Susan Lamb, Justine Keay, and Nick Xenophon Team MP Rebekha Sharkie resigns.[27]
