The leader of Australia's Labor Party is refusing to prove he's not a dual citizen.

Papers owned by the company News Limited have approached every member of the Senate, asking them to show with documentation they're entitled to be in Parliament.

Australia Correspondent Steve Price told Mike Hosking a number of MPs ave refused.

"The most high profile of all of this is Bill Shorten whose dad was a POM. Bill Shorten has also refused to give documentation and says he's not going to do it so it just gets worse."

So far the citizenship scandal has seen three MPs resign, and the High Court is investigating the eligibility of another five.

Price said the citizenship saga is getting worse by the day.

"They've gone particularly to those whose parents are born overseas. Twenty of them have refused to give them that documentation."

LISTEN ABOVE AS STEVE PRICE SPEAKS WITH MIKE HOSKING