The Turnbull government threats to use its numbers in the House of Representatives to refer two Labor members to the High Court over their citizenship status is a sign of desperation, the opposition says.
Leader of the House Christopher Pyne says there are still questions over whether Labor MPs Justine Keay and Susan Lamb, as well as crossbencher Rebekha Sharkie, held dual citizenship at the time of the 2016 election.
Mr Pyne says the government will put it to the vote if necessary when the lower house sits at the end of November if Opposition Leader Bill Shorten and Labor do not take any action.
"There is absolutely no reason the parliament should not vote to refer those members to the high court if the Labor party refuses to do the right thing," Mr Pyne told Sky News on Sunday.
Prime Minister Malcolm Turnbull said Mr Shorten seems to think the constitution does not apply to the Labor Party.
"I just say to Bill Shorten, it is the High Court of Australia and nobody else that determines whether MPs and senators can sit in the parliament, and he should stop running a protection racket for his MPs," Mr Turnbull told reporters during a brief visit to Hong Kong.
Manager of Opposition Business Tony Burke described it as a "desperate born-to-rule approach".
He said it wasn't that long ago Attorney-General George Brandis spoke against the approach Mr Pyne and the prime minister are now advocating.
"He said that sort of approach would be dangerous, and now it's government policy," Mr Burke told reporters in Sydney.
The threat came after Liberal MP John Alexander on Saturday resigned from parliament after admitting it was "most likely" he holds UK citizenship.
The member for Bennelong said he'll stand again for parliament in an upcoming by-election in a seat the Liberals hold by more than nine per cent.
Labor frontbencher Richard Marles said unlike Mr Alexander, Ms Keay and Ms Lamb took steps to renounce their foreign citizenship prior to nominations.
