Greens' Larissa Waters makes Senate return

Greens senator Larissa Waters is the first federal politician to make a comeback after being disqualified for holding dual citizenship.

Senator Waters was sworn in on Monday a little more than a year after she quit parliament when it was revealed she held Canadian citizenship.

"Admit the senator - or re-admit as the case may be," Senate President Scott Ryan told the upper house.

She had resigned in July last year after it was discovered she held dual citizenship because she was born in Winnipeg, Manitoba, putting her in breach of section 44 of the Australian constitution.

Senator Waters, a former co-deputy leader of the Australian Greens, was first elected in 2010 to represent Queensland and won a second term in 2016.

She replaced former Democrats leader Andrew Bartlett, who will run for the Greens in the lower house seat of Brisbane at the next federal election.