Three Labor MPs resign over citizenship

Labor has lost three lower house MPs within 10 minutes in a series of swift dual citizenship resignations from federal parliament.

Backbenchers Justine Keay, Josh Wilson and Susan Lamb told parliament on Wednesday the High Court's disqualification of their Senate colleague Katy Gallagher had changed the understanding of dual citizenship and eligibility laws.

"Until today's decision the reasonable steps test had been accepted for more than 25 years in this country," Mr Wilson said.

All three fell foul of a constitutional requirement that prospective MPs renounce their foreign citizenship before nominating to enter federal parliament.

Surrounded by colleagues, each indicated they would contest their seats in by-elections.

"I am not done yet. I intend to be back," Ms Lamb said.

While she made it clear her speech was not a valedictory, Ms Keay took a moment to list her career highlights before announcing her decision.

"I want to make it very clear to every member of my community and every member of this house that I am not done working and fighting on behalf of those who sent me here," she said.