The Labor Caucus will meet on Tuesday 31/05 and select the Ministry which will be sworn-in on Wednesday 01/06.
The process for selecting the Ministry is prescribed in the Caucus rules which say that the Caucus selects the members and the Prime Minister allocates portfolios. Even when Kevin Rudd notably departed from this process in 2007 and announced the Ministry ahead of the Caucus meeting the Caucus still had to endorse his selection.
We are expecting there to be 103 Labor MPs in the House of Representatives and the Senate, 54 belong to the Right, 47 are in the Left and two are factionally unaligned.
The Left is currently allocated 14 of the 30 seats in the ministry on a proportional basis and the Right receives 16. The new MP's shouldn't change this allocation. The Left chooses its 14 Ministers from a national list of MPs, while the Right decides its Ministerial spots using a state-based quota formula. The NSW Right usually gets six spots, the Victorian Right four, the Queensland Right gets two and SA, WA, Tasmania, ACT and the NT are treated as one ’small states bloc' – and they take the remaining four spots.
WA has done particularly well this election and will almost double its delegation from 5 MP’s to 9 and an additional Senator. This means that they will likely be asking for an additional seat on the front bench.
On top of all this the Labor Party needs to create a gender balance of the Ministry, an appropriate distribution between the House and Senate, geographic distribution, and a balance of its senior leadership team none of which is helped by the loss of two women frontbenchers in Kristina Keneally and Terri Butler (one each from the Right and Left).
The Morrison Government had increased the Ministry to 34 and Prime Minister Albanese may choose to keep some or all of those additional Ministers to give himself extra room accommodate the various considerations that he has to weigh up.