The Commerce Commission has laid 29 charges against Steel and Tube for making false and misleading representations about its steel mesh.
The company confirmed in December that it was one of three companies who were facing criminal charges from the commission after an investigation into sub-standard steel mesh.
In a statement released today, the Commerce Commission said the charges were filed in the Auckland District Court under the Fair Trading Act 1986.
They relate to conduct between 1 March 2012 and 6 April 2016, about a Steel and Tube product known as SE62.
"The charges allege that Steel and Tube made misleading representations on their batch tags, batch test certificates, advertising collateral and website that SE62 was 500E grade steel, when it was not," the commission said.
It's also alleged that Steel and Tube claimed SE62 had been independently tested and certified - including using the logo of an independent testing laboratory - when it had not.
The commission said Timber King Limited and NZ Steel Distributor were also charged over misleading claims around 500E steel mesh. They have entered guilty pleas and will be sentenced in August.
Steel and Tube said it was working with the commission for an appropriate resolution of the charges, but said it stood behind its products.
The commission said it expected to lay charges against one other company, and was investigating another additional company.
Building Minister Nick Smith said it was crucial building-product claims could be backed up.
"In this case the claim is it was not, and building material suppliers, such as steel, need to ensure that their product claims are correct - and where they are not that they are held accountable."