Labor and the crossbench do not require an absolute majority to pass Kerryn Phelps’ bill mandating medical transfers from offshore detention and other legislation opposed by the government, according to a leading academic.

In an essay on the Australian Public Law blog, Prof Anne Twomey argues that a simple majority of 75 MPs or fewer could change standing orders which currently require an absolute majority of 76 MPs to bring private member’s bills to a vote.

That would give Labor and the crossbench an easier path to pass a raft of bills opposed by the Morrison government.

Those include bills to ban live sheep exports, set up a federal independent commission against corruption, ban taxpayer funds being used to support new coal power plants, and remove exemptions that allow religious schools to discriminate against LGBT students.

Parliament is set to return on 12 February for the only two sitting weeks before the April budget, during which the Morrison government is at risk of losing a vote on the Phelps bill.

The Morrison government, which lost the Coalition’s majority when Malcolm Turnbull quit and Phelps won the Wentworth byelection in October, has attempted to head off the possibility of a historic defeat by promising a medical panel to give non-binding feedback on transfers.

Scott Morrison dialed up the pressure on Tuesday evening, labeling the Phelps bill “stupid” and accusing Labor of “selling out our border protection to get a cheap opportunistic win in the parliament”.

“[Bill Shorten] can have it – I’ll stay on the side of strong border protection and he can take a running jump,” he told Sky News.

Labor – which has already voted to support the Phelps bill provisions – earlier indicated it is open to the government’s proposed reform but sceptical.

Bill Shorten told reporters on Tuesday that Labor will both “work with the crossbench” and “listen to the government”.

“But I’m not convinced that when it comes to the health of anyone in our care that a bureaucrat in the department of home affairs is better placed to judge that person’s health than a treating medical doctor and specialist.”

Independent MPs are so far also unswayed – although the retiring Indi MP Cathy McGowan’s vote is unclear – meaning Labor and the crossbench could combine for an absolute majority of 76 in the lower house.

But Twomey argued that standing order 47 – which requires an absolute majority to suspend standing orders and bring a private member’s bill for a vote – may be in breach of section 40 of the constitution, which states questions are decided by a majority.

Given the Speaker only votes in the event of a tie, a simple majority is 75, or fewer if some members are absent.

The constitution also allows parliament to set its own rules, but Twomey argues that the “consensus” of eminent jurists – including the former solicitor general and now high court justice Stephen Gageler – is that those rules don’t override section 40.

Although the high court would be unlikely to rule on such a question, Twomey argued the result is that “the absolute majority requirement in the standing orders only has effect so long as a simple majority of the house chooses to accept its application”.

“The requirement for an absolute majority to pass a vote to suspend standing orders is not as great an impediment as it appears.”

Twomey suggested the rule for an absolute majority may prevent disruption of parliamentary business and major parties “may see value in maintaining support for such a standing order in the long-term”.

“It is, however, a matter for the House to determine, by a simple majority.”

A further complication is that the book of House of Representatives practice states that defeat on a major piece of legislation which the government has declared to be of vital importance could be considered a vote of no confidence in the government itself.

Morrison and the home affairs minister, Peter Dutton, have repeatedly elevated the importance of the Phelps bill, by arguing its passage would effectively dismantle offshore detention, although the crossbench does not believe it would bring down the government.

On Tuesday the finance minister, Mathias Cormann, said that the Coalition “obviously believes that we continue to enjoy the confidence and supply in the House of Representatives”.

“I mean, we have been, the Morrison government has been, a minority government from day one,” he told ABC24.

Cormann said that maintaining the confidence of the house was “quite a separate question” from the possibility of losing one vote.

Asked whether a loss on the Phelps bill could trigger an early election, Cormann dismissed the idea as “a lot of hypotheticals”. “Our intention is to hold the election in May,” he said.