Builders were encouraged to be more straight-talking at the Institute of Building conference in Auckland this week.
Tony Sewell, Ngai Tahu Property chief executive, said the development sector suffered from a bad reputation.
"You need to sort out who's who in the zoo," Sewell said.
If a developer was seeking 100 per cent finance, "you're working for the bank and they're not long-term players", Sewell said.
"Developers are not all in the same bag and the property industry suffers very badly from opportunists."
"We're all too humble," he said, attacking builders for promising short work time-frames.
Sewell said he did not want to commission a new building which went up fast but suffered defects.
A builder who gave an 18-month time-frame versus one giving a two-year build period left him wondering "what's the 18-month guy missed out?".
Honesty was critical, he said.
Sewell criticised main contractors for blaming subcontractors, saying as a client, he had only one contract and that was with the main contractor and he did not want to hear of issues with subcontractors.
Richard Aitken, Beca Group executive chairman, encouraged a more collaborative approach between developers, builders, consultants and owners: if they met at the outset and formed a team, the outcome was far more successful than a silo or segregated approach.
Sara Fox, project director for Swiss Re's The Gherkin office tower in London, said she would not let a tenant decide on the facade treatment or the core building services.
Roger Blakeley, Auckland Council chief planner, told the builders: "You people hold the key to unlocking the puzzle. We need a huge shift upwards. It needs a quantum shift."