Ben Carroll was sworn in as Premier of Victoria on Tuesday, hours after Jacinta Allan resigned rather than contest a caucus ballot she was expected to lose. His first announcement was a royal commission into the state's construction sector.

Carroll, until Tuesday the deputy premier and education minister, was elected at a party room meeting in Melbourne. Cabinet minister Sonya Kilkenny nominated late and drew the support of 15 MPs, Allan among them. Carroll took more than two thirds of the room. Caucus whip Juliana Addison then read the result as unanimous: "Ben Carroll has been unanimously elected for the Parliamentary Labor Party as our next Premier of Victoria."

Gabrielle Williams was elected deputy, defeating Steve Dimopoulos.

Let me make one thing very clear: I am not Daniel Andrews. I am not Jacinta Allan," Carroll said after the vote. "I will do things differently, because different times require a new approach. In my government, integrity will not be optional." Asked about his June undertaking not to challenge Allan, Carroll said circumstances had changed in the six weeks since.

The royal commission will examine a construction sector that has carried corruption allegations through two premierships, much of it attached to the state's Big Build program. Allan rejected calls for a commission repeatedly while in office. Carroll also committed to strengthening the Independent Broad-based Anti-corruption Commission, Victoria's integrity agency, though he did not set out what additional powers or funding it would receive. Terms of reference for the commission have not been published.

Allan left with a tally. "I stepped down after 1,036 days in this role," she said. "Not one of them wasted, not one of them easy." She said she believed she would have won a ballot of rank-and-file members but would not put the party through the wait. Under Victorian Labor rules a contested leadership goes to both caucus and the membership, a process that runs a minimum of 29 days. Kilkenny's withdrawal removed that requirement.

Carroll is the second Victorian premier in three years to take the job between elections. Daniel Andrews resigned in September 2023 and Allan succeeded him without facing voters as leader. Carroll now has four months. The state election is on 28 November.

The polling that moved the caucus has both major parties short of a majority. A Resolve Strategic survey of 1,000 Victorians published this month put Labor's primary vote at 27 per cent, the Coalition on 27, One Nation on 22 and the Greens on 12. A seat-level model by RedBridge Group, commissioned by Victorian Trades Hall from a sample of 6,500, put One Nation ahead of both major parties on 27 per cent. Its median projection gave the Coalition 39 seats of the 88 in the Legislative Assembly, Labor 35 and One Nation 12. Forty-five seats forms a majority.

Carroll grew up in Airport West in Melbourne's north-west and still lives there. His first job was at a local Kmart, where he joined the shop assistants' union. He worked as a lawyer for the Victorian government and as an adviser to former premier Steve Bracks before winning the seat of Niddrie at a 2012 by-election. He spent five years on the backbench, entered cabinet in 2017 with industry and employment, and later held public transport and roads. He belongs to the party's smaller right faction.

His education portfolio was not quiet. A 2024 VCE exam bungle affected 65 exams and ended with the curriculum authority's board sacked. He was unable to land a teacher pay deal, and the dispute produced statewide strikes.

Parliament returns with a new ministry to be sworn in and a royal commission to establish. Both will be running when Victorians vote in November.