Allowing communities to pre-select candidates was one of a number of key recommendations made after the party's heavy 2011 state election loss.
NSW Labor bosses want the process removed from the hands of factional powerbrokers and perceived "backroom" deals, in a bid to improve transparency and bolster Labor's community standing.
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The party was trialling the system in Sydney on Saturday, with inner-city residents invited to vote for one of five Labor candidates who will contest the mayoral election later this year.
"This is the Labor party reaching out, opening up our party and moving out of the back rooms and into the community to select our candidates," Mr Robertson told AAP.
He said about 4500 people had voted in the pre-selection process by midday (AEST) on Saturday.
The winner will try to topple Sydney Lord Mayor Clover Moore in September.
Mr Robertson said the system would be used to select at least five NSW Labor candidates for the next state election, which is due to be held in 2015.
"There are issues associated with cost in running these sorts of exercises," he said. "Obviously if we can do more we'll do more, but we'll do at least five."
