Greens senator Larissa Waters resigns over Canadian dual citizenship

Greens senator Larissa Waters has resigned from Federal Parliament over her dual citizenship with Canada.

The senator made international headlines and provoked debate after becoming the first woman to breastfeed her baby in parliament in May.

She said she had no idea she was a dual citizen after leaving Canada when just 11 months old.

"I left Canada as a baby, born to Australian parents studying and working briefly in Canada before they returned home," Ms Waters said in a statement.

"I have lived my life thinking that as a baby I was naturalised to be Australian and only Australian, and my parents told me that I had until age 21 to actively seek Canadian citizenship. At 21, I chose not to seek dual citizenship, and I have never even visited Canada since leaving at 11 months old."

Ms Waters said she sought legal advice following senator Scott Ludlam's resignation on Friday for holding a dual citizenship of Australia and New Zealand.

"However after Scott’s shock discovery was devastated to learn that because of 70-year-old Canadian laws I had been a dual citizen from birth, and that Canadian law changed a week after I was born and required me to have actively renounced Canadian citizenship," she said.

"I had not renounced since I was unaware that I was a dual citizen. Obviously this is something that I should have sought advice on when I first nominated for the Senate in 2007, and I take full responsibility for this grave mistake and oversight. I am deeply sorry for the impact that it will have."

Greens leader Senator Richard di Natale told the media on Tuesday he was gutted by Ms Waters' resignation.

"I am gutted by today's announcement coming just a few days after Scott's announcement," he said.

"Larissa has been an incredible representative for the people of Queensland and indeed for the nation. She has been a wonderful Deputy and her departure is deeply saddening."

Asked if any other members of the Greens were born overseas he said: "We have ensured that we check and double-check that everybody else is not in this situation and the last thing I want to be doing is standing here again with another announcement."

Senator di Natale said it had been a "terrible month" for the Greens.

"There is no other way of sugar coating it," he said.

"To lose two people like Scott Ludlam and Senator Larissa Waters, these are two of the most outstanding people, not just in the parliament but I would say in politics anywhere in the country."

Last month Ms Waters was accused of being an exhibitionist and was trolled for becoming the first woman in parliament to breastfeed while passing a movement.

An anonymous trol sent a message to the senator saying it was "not a good look" and labelled her a "dumb b****".

But he senator appeared unfazed by the criticism sharing the message with the comment "Lol "Regards"."

More than 100 users responded to the troll's message, with many standing up for the senator.

"Please know you're inspiring the rest of us to be brave and never give up," one user wrote.

Another said: "Keep doing what you are doing @larissawaters - challenge stereotypes and leading by example".