SYDNEY (Reuters) - Australian Prime Minister Malcolm Turnbull announced plans on Monday to force all lawmakers to declare they are not dual nationals as he seeks to defuse a political crisis that saw his deputy ejected from parliament.

Australian Prime Minister Malcolm Turnbull reacts as he walks with officials and security personnel to a media conference announcing Australia's national security plan to protect public places in central Sydney, Australia, August 20, 2017. REUTERS/David Gray

Turnbull’s center-right coalition government was thrown into disarray last month when the High Court ruled that five lawmakers who were dual nationals, including Deputy Prime Minister Barnaby Joyce, were ineligible for parliament.

The Australian leader has been facing down calls since for a full audit of parliamentarians to ensure they comply with the country’s constitution, which bars foreign nationals from sitting in parliament to prevent split allegiances.

The High Court ruling expelled three members of the Liberal-National coalition government from parliament, while a fourth resigned days later after confirming he also had dual nationality. The other affected lawmakers were from minority parties, with the main opposition Labor Party yet to be ensnared.

Turnbull said his plan, unlike an audit, would put the onus on lawmakers to check their own situation and anybody found to have made a false declaration would be in contempt of parliament. Lawmakers will be required to produce documents to prove any second citizenship has been renounced.

“Members and senators have been put squarely on notice now and so they will be turning their mind to their own affairs and the issues of citizenship,” Turnbull told reporters in Canberra.

The new laws would apply to both existing and prospective lawmakers. Those already in parliament would be given 21 days to make a declaration from the date it comes into force, while new lawmakers would have the same period of time from their swearing in.

Turnbull said he hoped to push the changes through parliament in the last remaining sitting days this year. That will require support from the Labor Party, which suggested a similar plan last week.

Turnbull has said previously that the court’s interpretation of the constitution was “very strict”. He has flagged potential changes to the constitution, noting that more than half of Australia’s population of 24 million was either born overseas or has a parent who was born overseas. A referendum would be needed to change the constitution.

All seven lawmakers in the High Court case, two of whom were cleared to remain in parliament, accepted that they were dual nationals at the time of their election but claimed they were unaware of their status. Some were conferred a second nationality by birth, others by descent.