Labor is seeking to rekindle the debate over Peter Dutton's eligibility to remain in Federal Parliament, seizing on new evidence suggesting a direct financial agreement between one of the Home Affairs Minister's childcare centres and the Commonwealth.

Key points: Peter Dutton's links to a family trust that owns childcare centres have raised concerns about a breach of section 44 of the constitution

Peter Dutton's links to a family trust that owns childcare centres have raised concerns about a breach of section 44 of the constitution New document shows agreement between one centre and Federal Government for funding a special needs teacher

New document shows agreement between one centre and Federal Government for funding a special needs teacher Shadow Attorney-General Mark Dreyfus says it adds weight to Labor's calls for High Court to determine Mr Dutton's eligibility to sit in Parliament

But even with the numbers in the House of Representatives precariously balanced in the wake of Malcolm Turnbull's resignation, any attempt by the Opposition to have Mr Dutton's case referred to the High Court would need the backing of a few Coalition MPs.

The Home Affairs Minister has vehemently denied he is in breach of section 44(v) of the constitution, which bans politicians benefitting financially from the Commonwealth.

His family trust has interests in two Brisbane childcare centres that receive government subsidies for the services they provide.

Legal advice obtained by Mr Dutton suggests that does not put him in breach of the constitution, because the subsidies are established by a law that affects centres across the country rather than individual agreements.

But a new document, seen by the ABC, reveals an agreement between one of those centres and the Federal Government for funding a special needs teacher for a child on the autism spectrum.

"This Approval letter, together with the Conditions of Funding, make up the agreement between the Commonwealth and You in relation to how the IDF subsidy, for which you have been approved, will be used," the letter said.

Shadow Attorney-General Mark Dreyfus said the document added more weight to Labor's calls for the High Court to determine his eligibility to sit in Parliament.

"This further document that's come to light makes it clear that there is an agreement between Mr Dutton's childcare centres and the Commonwealth, and that's why there is, we think it's clear, a breach of section 44 of the constitution," Mr Dreyfus told reporters in Melbourne.

He denied the merits of the agreement, providing specialist services for a child at the centre, should come into the debate.

"I don't think that we're even going to question of what the purpose of the Commonwealth funds is," he argued.

"The prohibition in the constitution is absolutely clear.

"If Mr Dutton, as a Member of Parliament, has a direct or indirect interest in a contract with the Commonwealth, then he is ineligible."

The nation's chief lawyer, Solicitor-General Stephen Donaghue QC, was called on to give his urgent advice on Mr Dutton's eligibility ahead of last month's leadership challenge.

He advised that the subsidy scheme would not render Mr Dutton ineligible to remain in Parliament, but further stated it was "impossible to state the position with certainty" as he did not have all the facts of Mr Dutton's business dealings before him.

Mr Dutton's office has been contacted for comment.