MPs spar as Susan Lamb faces calls to be referred to High Court

Labor has hit back at Turnbull government figures who continue to call for the dual citizenship status of MP Susan Lamb to be referred to the High Court for a ruling.

"What kind of people are they?" shadow attorney-general Mark Dreyfus told ABC radio on Thursday, a day after Ms Lamb tearfully revealed that because her mother walked out on her when she was six years old she can't prove her UK citizenship has been renounced.

"It's time we moved on from this."

The government is calling for the resignation of Ms Lamb - who narrowly won the Brisbane seat of Longman for Labor from the LNP at the 2016 election - because she has no evidence of renouncing her dual British citizenship by descent and is therefore constitutionally ineligible for parliament.

Labor leader Bill Shorten insists Ms Lamb took all reasonable steps to renounce her citizenship.

"I don't think anyone who is fair dinkum couldn't have been moved by what she said," Mr Shorten told reporters, calling again on the government to agree to a "job lot" referral of coalition and Labor MPs.

"I think Australians are rightly angry that we're still arguing about citizenship; it's as if the summer break never happened," he said.

Attorney-General Christian Porter said the MP's circumstances were not dissimilar to that of former Nationals deputy leader Fiona Nash who was ruled ineligible to sit in parliament by the High Court.

"This is an issue about where the law is," he said, acknowledging that government MPs were moved by Ms Lamb's experience.

"We can't change the position at law no matter how empathetic we are."

In an emotional explanation to parliament on Wednesday, Ms Lamb said she was unable to obtain a crucial copy of her parents' marriage certificate - which the UK Home Office requires to complete its paperwork - because of her estrangement from her mother.

"It's a complex and a traumatic story, a story that I don't usually share," she said.