Caucus members had 40 per cent of the final decision, party members also had 40 per cent and affiliates (unions) had 20 per cent.
With just 16 per cent of caucus votes in the first round, Mr Little had been lagging behind his main rival Mr Robertson, then on 44 per cent, but he was saved by strong support from the unions in the third round.
"It was difficult to choose an outcome [that would please everyone] and the result reflects that it was incredibly close."
Dr Jones said the appointment was a huge relief.
"Not relief in who the leader is necessarily, but relief that now we know who the leader is let's get on with it."
Dr Jones said Mr Little would be very pragmatic and brought a lot of organisational experience to the role to help rebuild the party. "I think people will be invigorated. It has been a month or two of uncertainty. It will be good to get back to work. The Labour party is still strong. We've actually gained new members since the election."
Dr Jones planned to meet with party members at a Tauranga Labour meeting today. "I expect it will be quite lively."
Tauranga National MP Simon Bridges congratulated Mr Little on the new role, which he said would not be easy.
"They are a deeply divided party and you can see that in the vote where he's become leader."
However, National would take him seriously. "He has led the biggest union in the country, so he's got some skills."
Shortly after the announcement yesterday, Mr Little said it was an immense privilege to lead Labour and to be given the task of ensuring it once again became a powerful force that backed New Zealanders in getting ahead as a nation.
"Labour is the party that has always been at the forefront of real and meaningful change that benefits all New Zealanders and that is the tradition I will honour as leader," he said.
Mr Little would not say who he would like as his deputy and wanted to talk to his colleagues before deciding who would be in what positions.
Who is Andrew Little?
• Andrew Little was elected to Parliament in 2011.
• Born in New Plymouth and educated at New Plymouth Boys' High School, he studied philosophy, law, and public policy at Victoria University. He served as president of Victoria's student association and was twice elected NZUSA president. While at university he flatted with actress Robyn Malcolm. His first job was as a solicitor for the Engineers Union (later EPMU), working on employment law and ACC issues.
• Appointed national secretary of the EPMU in 2000.