The Dairy Workers' Union has followed sister union EPMU by backing Andrew Little as next Labour leader -- delivering him almost half of the total union vote for the leadership contest.
Chris Flatt, the DWU national secretary, said the decision to endorse Little was unanimous on the union's executive.
"The Dairy Workers' Union support of Andrew Little is based on his deep involvement with union members and working people over many years and from the experience he brings from outside Parliament in leadership roles with the EPMU and as President of the Labour Party."
He said the executive weighed up the past experience of all four candidates, their efforts representing workers' interests and who was best placed to lead Labour into 2017 election.
As with the EPMU, that endorsement is not binding on the unions' delegates but amounts to a recommendation. The union vote is worth 20 per cent of the final tally while the members and caucus vote are worth 40 per cent each.