Premier Daniel Andrews’ Socialist Left powerbase has suffered a blow in a ballot deciding the ALP’s central decision-making body for the state, putting the faction in the back seat as a series of preselections approach.

Labor officials conducted a vote to decide the composition of the party’s 33-person State Administrative Committee on Tuesday night, resulting in a redraw of Labor's Victorian factional boundaries.

Mr Andrews’ Socialist Left faction scored 11 votes, a third of the total, while a new faction made up of the party’s right and an alliance with powerful industrial unions from the Left, including John Setka’s construction union, scored a near absolute majority of 21 votes.

The result confirms the ascent of Victorian Cabinet member Adem Somyurek as state Labor's pre-eminent factional powerbroker, just four years after he resigned from his ministerial position following an investigation into allegations he had bullied a member of his staff.