Labour's biggest affiliated union, the EPMU, has official thrown its weight behind former national secretary Andrew Little in the Labour leadership after failing to reach agreement in last year's contest.
The national executive unanimously backed Mr Little who was national secretary for 11 years and before that an employment lawyer.
But it is a recommendation only for a ballot which is secret and the rules ban bloc voting.
It will be a big boost to Mr Little's campaign. He is likely to get more union support, tacit if not explicit from some of the seven affiliated unions.
In the leadership contest last year between David Cunliffe, Grant Robertson and Shane Jones, the EPMU was divided with Auckland generally favouring Mr Cunliffe and Wellington generally favouring their home town candidate in Mr Robertson.