Attorney-General George Brandis has no sympathy for Scott Ludlam who he said had been extremely negligent when he ran for the Senate at three elections despite still being a New Zealand citizen,
Mr Ludlam resigned his West Australian senate seat on Friday when it was brought to his attention that he still held dual Australian-New Zealand citizenship, making him ineligible to hold office.
Senator Brandis noted Mr Ludlam had been "very ungracious" and "extremely mean-spirited" when former South Australian senator Bob Day was also found to be ineligible for election earlier this year.
"So I don't think we should shed too many tears over the consequences of Mr Ludlum's own negligence," he told Sky News on Sunday.
He expects the High Court will order a "countback" of the vote for the WA senate election last year, which will "almost certainly" result in the election of another Greens senator.
Senator Brandis said Mr Ludlam could face a substantial debt repayment for the salary and allowances he received during his tenure as a senator.
He said there is also a "100 pounds" fine for every day that a person not eligible to sit does sit in the Senate.
"Whether or not debt would be waived as it has been on previous occasions is a matter for the Special Minister of State, senator Scott Ryan," he said.
The former deputy Greens leader was first elected in 2007 and retained his West Australian seat at the 2013 and 2016 elections.