Julia Banks' abandonment of the Liberal Party leaves the federal government vulnerable to having Home Affairs Minister Peter Dutton referred to the High Court, with Labor working on the enlarged crossbench to convince them he has breached section 44 of the constitution.

But the government is not immediately in danger of falling, with Ms Banks pledging support on matters of supply and confidence, while Labor and the combined crossbench are still short of the numbers to bring on a vote on private members' legislation, such as the establishment of a federal anti-corruption body.