Five Australian lawmakers have been forced from Parliament in an ongoing legal wrangle over a 117-year-old constitutional ban on dual citizens standing for election.

Five by-elections that will result from the latest turmoil on Wednesday create opportunities for Prime Minister Malcolm Turnbull's conservative coalition to increase its single-seat majority in the House of Representatives, where parties need a majority to govern.

Opposition Sen. Katy Gallagher became a test case in the High Court in its interpretation of the ban on dual nationals being elected to Parliament.

Another four lawmakers quit after the court dismissed her.