Prime Minister Malcolm Turnbull admits that "only time will tell" whether the government's plans to strip dual national terrorists of their Australian citizenship will survive a High Court challenge.

His comments come as Labor demanded more time to study the latest version of the bill before waving it through, amid claims the opposition was given only an incomplete, half-hour briefing on the laws on Tuesday.

Persistent questions have circulated on whether the bill to strip citizenship is constitutional. The government says it has advice from the Solicitor-General that the legislation would likely survive a High Court challenge but has refused to release that advice.

Mr Turnbull said while the government was confident it would survive a challenge, such legal advice could not be categorical.

"The government's advice is that the laws, if challenged in the High Court, would be upheld. But of course, advice isn't always borne out," Mr Turnbull said on Wednesday in Canberra.

"The High Court makes the law in many respects, as you know. It's the ultimate court as it interprets the constitution. Having said that … [The bill has] gone through a proper process now, and we are confident that it would survive a High Court challenge, but only time will tell."

Constitutional law experts and Labor have expressed concerns about whether all aspects of the law are constitutional, in particular the limited retrospectivity. The law would be backdated for terrorists who have been sentenced to at least 10 years' jail in the past 10 years, which would mean citizenship could be stripped from some notorious terrorist inmates.

Attorney-General George Brandis wrote to his shadow counterpart Mark Dreyfus in August stating that Solicitor-General Justin Gleeson believed "there is a good prospect that a majority of the High Court would reject a constitutional challenge to the core aspects of the draft bill".

Meanwhile, Labor warned the government not to rush the legislation through Parliament. The bill was scheduled to be debated on Wednesday but Labor sources said that as of Tuesday night they were still in the dark on the revised details.

The government has made 26 changes based on recommendations from a cross-party committee of MPs that will significantly tighten the scope of the bill, in particular ruling out stripping citizenship from people who are still in Australia but have not been convicted of any terrorism crime.

While that should secure the opposition's support, Labor has insisted on making sure the recommendations are properly reflected in the new legislation.

Labor sources said immigration spokesman Richard Marles was given a briefing by the government on Tuesday afternoon that lasted just half an hour and only covered 12 of the 26 planned changes.

This is despite the fact the bill was scheduled for debate on Wednesday morning.

Manager of opposition business Tony Burke then told Parliament on Wednesday morning that Labor was not ready to debate the legislation.

It is now unlikely to pass Parliament before the next sitting week, which begins November 23.

Justice Minister Michael Keenan said the legislation was "hardly a surprise" and Labor could not expect "unlimited time" to consider it.

But he added: "If the opposition needs more information, we're happy to provide it. But the sooner we pass it, as far as I'm concerned, the better."

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