New evidence proves it has become "completely untenable" for Peter Dutton to avoid the High Court over his personal stake in two publicly-funded child care centres, federal Labor says.
Opposition frontbencher Jim Chalmers claims a letter, which has come to light in recent days, casts more doubt on the home affairs minister's eligibility to remain in parliament.
"It's become completely untenable for Scott Morrison not to refer Peter Dutton to the High Court," Mr Chalmers told Sky News on Thursday.
The letter shows one of the Brisbane child care centre held by Mr Dutton in trust had a funding agreement with the Commonwealth to allow the hiring of a special needs teacher.
Late last month, a Labor attempt in parliament to force Mr Dutton to the High Court was lost by just one vote.
The opposition believes it has the lower house numbers to try again when parliament returns next week, with Labor MP Emma Husar returning after personal leave.
"Scott Morrison should exercise some leadership and refer it to the High Court. There are so many unanswered questions about Peter Dutton's eligibility to sit," Mr Chalmers said.
"When the parliament is on a knife-edge, as it is, that calls into question all kinds of decisions this Morrison cabinet will make."
Shadow attorney-general Mark Dreyfus said the minister was "quite probably" ineligible to sit in parliament, particularly given the solicitor-general recently said there was some doubt surrounding his standing.
Labor MP Mark Dreyfus (File) Source: AAP
Mr Dreyfus said the minister's eligibility could call into question thousands of decisions he has made as immigration and home affairs minister.
"It's a significant matter also because this is a government that is hanging by a thread to control of the House of Representatives," he told reporters in Melbourne.
"It is extremely significant that one of its most senior members, Peter Dutton, is quite probably ineligible to sit in the parliament."
The constitution bans from parliament anyone with a direct or indirect financial interest in Commonwealth assets, given it may create a conflict of interest.
