"Quite clearly New Zealanders didn't respond to our messages. I don't think we can just look at the campaign, I think we have to look at the whole last three years and see why it is what I think is a good policy platform isn't reaching to New Zealanders," Mr Robertson told TV3's Firstline this morning.
"Leadership's just one factor among many. We need to look at the way we talk about issues, what issues we talk about, the way we present ourselves across our whole three year term and leadership will form part of those considerations."
It was important the party listened to its members and other New Zealanders, Mr Robertson said.
"I think about the hundreds and hundreds of activists around New Zealand who've worked so hard over the last few months for us - we have an obligation to take some time now to look at the result and say 'what could we do differently' because the worst result in 92 years is something that we have to take very seriously.
"There were a lot of distractions during the actual campaign period and the people were talking a lot about those and perhaps our policy platform wasn't getting through as well as it might."
Mr Robertson didn't rule out a entering a leadership challenge.
Labour's constitution states that within three months of a general election there has to be a vote of confidence for the leader within the caucus.
"I'm not doing anything in advance of that vote. I'm listening to people, I'm listening to members of the party, to our affiliated unions and to the public and we'll make some decisions on that as a caucus when that vote occurs," he said.
"What we have to deal with is this result. I'm very disappointed about it, I know that others in the party are disappointed about it and we need to listen to the New Zealanders who have previously voted for us and now aren't.
By Brendan Manning of APNZ
