Voters should be considering Labor's part in the citizenship fiasco as they go to the ballot box in by-elections, Treasurer Scott Morrison says.
But he confirmed the Liberals won't run a candidate in Perth, which Labor holds with just a 2.2 per cent margin, or in the safe Labor seat of Fremantle.
Instead, the treasurer says, the government is focused on the Queensland electorate of Longman and the Tasmanian electorate of Braddon, as well as a state by-election in WA.
"I would ask voters, in particular, in Longman and Braddon where the Labor Party have the standing members, to think about (the citizenship drama)," Mr Morrison told reporters in Sydney on Friday.
"They can't be trusted on this stuff."
The by-elections were sparked when the High Court ruled Senator Katy Gallagher was a British citizen when she was elected, forcing other MPs in the lower house to resign.
Mr Morrison said the Liberals aren't running in Perth or Fremantle because they're long-time Labor seats.
But the Liberals are running Georgina Downer in the South Australian seat of Mayo, where the Greens have announced Major "Moogy" Sumner will be their candidate against incumbent Rebekha Sharkie.
Labor MP Emma Husar has also had to deny she's entitled to Polish citizenship after coming under attack for not providing documented proof.
Ms Husar says she wrote to the Polish consulate to renounce any entitlement through her Poland-born paternal grandparents 16 days before her nomination for federal parliament in 2016.
But Attorney-General Christian Porter says Ms Husar had not put on the citizenship register any documented evidence her renouncement was accepted.
Ms Husar told The Australian on Friday she had nothing more to add.
"You have to have something to renounce. You have to have something in order to give it back. I am not a dual citizen," she said.
Under new rules set to be introduced before the by-elections, candidates have to give their citizenship information to the Australian Electoral Commission.
It will then be made public, but the AEC won't be given the power to adjudicate the eligibility of candidates.
A cross-party committee of MPs has called for a referendum to end the ban on dual citizens entering parliament, but Prime Minister Malcolm Turnbull says there is no time before the next general election.