"It's obviously Senator Ludlam's oversight", told reporters on the Gold Coast on Saturday.
Greens poster boy and renowned good hair-haver Scott Ludlam tendered his surprise resignation yesterday, when it was revealed that he holds dual citizenship with New Zealand, and is therefore ineligible to hold a seat in the Senate.
"In the past, the rule has been that they've waived that, Senator Ludlam has worked as a senator, carried out the functions, done constituency work, he's attended parliament, so he's done all the work", said Green.
It then took Senator Ludlam's office several days to contact the High Commission in New Zealand and verify the information was correct.
"I have no wish to draw out the uncertainty or create a lengthy legal dispute, particularly when the Constitution is so clear".
Born in New Zealand in 1970, Mr Ludlam left the country to settle in Australia when he was three years old. Under section 44 of the constitution, anyone who "is under any acknowledgement of allegiance, obedience, or adherence to a foreign power" can not stand for parliament.
The Greens co-deputy leader is the third senator to fall foul of the Consitution in this term of parliament, with South Australia senator Bob Day resigning in November a year ago after his building company went into liquidation. I am resigning as Senator for Western Australia and Co-Deputy Leader of the Australian Greens, effective today.
He settled in Australia not long before his ninth birthday, before being naturalised when he was in his mid-teens.More news: G20 communique exposes divide with US on climate policy
"This is entirely on me and I should have addressed it in 2006", he said.
On Friday, Mr Ludlam quit after accepting he had been ineligible to be a senator since his election in 2008.
'Scott has been an outstanding member of the parliament and of the Greens, ' he said in a statement.
If as anticipated, the court finds Mr Ludlam's election was ineligible, the Department of Finance and Senate will calculate the debt from salaries, travel allowance, office costs and benefits he received during his parliamentary career.
Mr Ludlam's position will be filed by a recount of ballot papers from the 2016 election, leading to the possible election of 22-year-old Jordan Steel-John who was third on the Greens Senate ticket.
Mr Steele-John, who has cerebral palsy, had to give up his British citizenship to run for parliament back in 2013.
"We will petition them if they come after us for the kind of relief that was offered to senators Day and Culleton", he said.
Fellow Western Australian and former One Nation senator Rod Culleton was booted from the Senate earlier this year after a Federal Court ruled his business has gone bankrupt.