UPDATED 4.19PM: Fresh endorsements for the frontrunners of Labour's leadership race - from a former prime minister and a major voting union.

Sir Geoffrey Palmer has given his backing to his local MP, Grant Robertson - saying he's the right generation, he's the best debater in the party, and he has the qualities needed to lead.

And the Dairy Workers' Union has recommended its delegates vote for Andrew Little.

National secretary Chris Flatt says Mr Little is a fantastic leader, and while he's softly spoken, he can bring people together and has "steely determination" around people's rights.