Text messages and letters reveal a behind-the-scenes struggle to pass the coalition government's contentious Fast-track Approvals Bill, despite concerns it broke Parliament's rules about benefiting private companies.

The government was warned that including private projects like mining and housing in the legislation would make it inadmissible as a government bill, as only private bills can benefit private entities.

The conflict was only resolved after Speaker of the House, National's Gerry Brownlee, ignored official advice to make the bill law anyway.

One legal expert says Brownlee's decision was "borderline", and allowed companies to side-step an avenue for legal challenges.

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Labour and the Greens criticised the move as "unprecedented" and potentially dangerous, fearing it sets a precedent for including private companies in government legislation.

Brownlee defended his decision, saying many bills have private benefits and the projects still have to be approved by an expert panel.

Documents obtained by RNZ reveal the Office of the Clerk - government's official rule-keeper - first warned Minister Chris Bishop about the potential breach in July last year.

The Office of the Clerk told Bishop that including private projects in the legislation would make it inadmissible as a government bill, as only private bills can benefit private entities.

The bill's amendment paper, which included the project list, was specifically designed to "fast-track" 149 projects seen to be important national or regional infrastructure, including many from private companies. These projects could skip a referral process and move straight to consideration by expert panels.

Already dogged by public controversy and protest, the documents show the bill was also subject to an internal stoush as the government rushed the bill through Parliament late last year.

After Bishop did not respond to its initial concerns, the Clerk reiterated its advice in a long October letter.

On 3 October, Bishop text messaged Brownlee: "Can I talk to you re fast track.

Brownlee replies: "Bish, can I suggest you don't chase procedure advice until I come back to you. I film [sic] try to get a clear position once material cones [sic] through.

Bishop told Brownlee the Clerk's view had, "come as a surprise".

When questioned about the process, Bishop told RNZ that he directed officials to address the Clerk's concerns, and said he was subsequently advised that the issues had been "resolved."

The Clerk of the House Dr David Wilson declined to comment on whether his office had altered its position, citing the confidentiality of ministerial advice.

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The Clerk's letter to Bishop did include a suggested course of action if Bishop was determined to include a list of companies in the bill: A motion to suspend standing orders.The Clerk's letter said this approach would be a "significant step" but would "preserve the distinction between public and private legislation".

Instead of following this advice, the Speaker chose to disagree with the Clerk and Assistant Speaker and allow the list to be included in the bill.

Borderline call

Brownlee referred to his final decision as finely balanced. "Virtually no bill passed in this House that doesn't have some private benefit," he concluded. He also argued that inclusion in the bill wasn't a slam-dunk, as companies still needed to gain final approval from an expert panel.

But according to legal expert Professor Andrew Geddis the move marked a rare, if not unprecedented, break with parliamentary precedent. He could not recall a similar instance of a Speaker rejecting the advice of both the Clerk and Assistant Speaker, Geddis said.

"You could quite easily write a Speaker's ruling that came out the other way, put it that way," Geddis said, labelling the decision "borderline". "It's just unfortunate the call he made happened to help out his party and the people he sits alongside with in government."

Geddis said the inclusion of the list of projects in the bill sped up the process in two ways.

As well as skipping the referral stage, where projects need to be referred for fast-tracking by the Minister for Infrastructure, projects included in the bill could avoid potential legal challenges about their inclusion in the Fast-track pathway.

"Including these projects in the statutory schedule wrapped the protection of parliamentary privilege around the ministerial decision to send them to an expert panel, thereby preventing any attempt to have the courts judicially review the basis for that decision," he said.

While some of the 149 projects are government projects, many are projects put forward by companies, including a gold mine, housing developments and energy generation. Some of the projects listed include projects which have previously been rejected by courts, including a seabed mining project, and a revival of the Ruataniwha Dam scheme under a different name.

Brownlee's decision to disregard the Clerk's advice prompted the Labour Party to declare it had lost confidence in him.

Labour's Shadow Leader of the House Kieran McAnulty called Brownlee's decision "unprecedented".

"It has raised serious constitutional questions about the passing of a government bill that provides for private benefit."

Green Party environment spokesperson Lan Pham criticised Bishop for inaction, arguing the Speaker's decision could have been avoided if Bishop had acted sooner.

"I think it's completely negligent of the Minister to have known about the potential in admissibility of this amendment paper for months, and then not only having not bothered to address the advice, but actually sitting on his hands, and then instead lobbying the Speaker at the last minute."

Pham described the situation as "dangerous," fearing it sets a precedent for including private companies in government legislation.

"We're expecting to see this again when the government tries to write legislation that justifies allowing a specific set of commercial fishers to fish the high protection areas of the Hauraki Gulf."