Read more: Transpower's power pole proposal will only shift problem, say residents of Maungatapu in Tauranga
Maungatapu residents fight Transpower power pole realignment proposal
He said Gardner-Hopkins had represented Transpower for a number of years in "significant" cases.
Beatson said his opponent had "what amounts to a conflict of interest" and information that could give him an advantage.
That included being familiar with Transpower's expert witnesses and holding strategic or personal information as well as potentially confidential information.
Gardner-Hopkins, a former partner at Russell McVeigh, acknowledged the concern had been raised and said he took a "different position" to Transpower on what was "appropriate and required in terms of professional conduct".
Both lawyers agreed the commissioners could not resolve the disagreement and Gardner-Hopkins continued to give his evidence.
Beatson said Transpower would consider pursuing the conflict matter through other avenues, such as court, but for now, he wanted the company's objection recorded.
Gardner-Hopkins submitted that the consents should be declined, largely focusing on technical legal arguments about how relevant policies and case law could apply.
He argued the adverse effects of Transpower's proposal were more significant than the state-owned enterprise had claimed, and positive impacts for one group of people should not be used to outweigh negative impacts for another.
Beatson said he disagreed with Gardner-Hopkins' policy and case law interpretations and that he would reply in detail in writing so the hearing would not run into a third day.
Transpower made resource consent applications to move a 3.3km portion of a 110kV transmission line to align with State Highway 29A between Maungatapu and Matapihi.
The line is one of two supplying power to Mount Maunganui.
The move has been welcomed by some Maungatapu residents because it would mean the removal of power lines currently slung directly above about 24 homes and a park.
Other residents support moving the lines away from houses but strongly oppose Transpower's replacement plan.
They say the proposed installation along the highway of 18 new poles - the largest two of which will be 35m and 45m high built either side of the estuary - and lines will blight vistas and drive down property values.
The hearing was adjourned. Transpower was given until August 3 to prepare responses to submissions.
A decision will be due within 15 working days of the commissioners closing the hearing.