The New Zealand Transport Agency (NZTA) is refusing to name the company which manufactured the failed steel used in the Huntly Bypass or the laboratory that tested and passed it.
NZTA has rejected Official Information Act (OIA) applications by RNZ, aimed at finding out more about what went wrong with failed steel at four bridges on the bypass on the Waikato Expressway, citing commercial reasons.
The Crown agency and its contractors have not challenged RNZ's reports that steel from China for the bridge piles was cheap and brittle, forcing a redesign of the $450 million bypass.
But it will not disclose the name of the steel mill and the fabricator, nor the laboratory which carried out the tests that said the steel was acceptable.
The NZTA's answers do reveal it has no record of any written approval being given by the agency's engineer for the New Zealand supplier Steel and Tube to import the pile casings, or for the contractors to begin driving the piles into the ground.
The government has said it has no concerns about the steel either in Huntly or at the Waterview Connection project in west Auckland, where only half the New Zealand standard was specified for vital steel strand.
Labour Party building and construction spokesperson Phil Twyford wants to know why more details won't be revealed if nothing is wrong.
"The transport agency's response shows an appalling lack of accountability," Mr Twyford said.
"The worry here is that the contractors involved may well be buying the cheapest steel available and I think that the public would want to know that there's an adequate consideration of the whole value of the project, with public safety being right at the top of the list."
NZTA rejected the official information requests principally on the grounds that negotiations were going on, including between Steel and Tube and its supplier in China, and that the information could unreasonably prejudice a commercial position.
"I would have thought there are plenty of ways to protect commercial confidentiality by the way that information is released, said Mr Twyford.
"The priority that should be given to reassuring the public that major construction projects are safe, that risks haven't been taken because of inadequate or improperly implemented certification processes. I would have thought that trumps commercial sensitivity any day of the week."
Green Party transport spokesperson Julianne Genter said it raised serious questions about other projects.
"It's absolutely in the public interest that we understand exactly what went wrong with the steel procurement for the Huntly project and what might be going wrong in our other processes for other public works projects," she said.
"It's not good enough to be assuring everyone that it is safe while refusing to release any information about when the steel was tested and how it ended up getting procured, and actually started to get installed in a process when it wasn't up to scratch."
NZTA did release three pages of project specifications for Huntly, most of which relate to structural steel, not the pile casings.
Other steel failures are coming to light, accompanied by more obstacles to reporting on them.
Lyttelton Port Company has told RNZ it is not subject to either the OIA or Local Government information laws so doesn't have to talk about how its huge wharf piles imported for earthquake repairs turned out to be substandard.
It has confirmed it was refunded for the piles, destined for the Cashin One wharf after the September 2010 quake, and has since insisted on rigourous steel testing for tens of millions of dollars of other wharf rebuilding.