Dunedin's 1902 courthouse is the subject of a draft business plan due before Cabinet within the next two weeks.
That plan stipulates at least $15 million is needed to strengthen the building - a figure widely ridiculed by Dunedin experts.
In response to that reaction, Dunedin-based Police Minister Michael Woodhouse organised a secret meeting, held in the city last week, which brought engineers representing the Ministry of Justice together with Dunedin engineers.
But the meeting's participants were forced to sign watertight confidentiality agreements before the meeting took place.
That was not good enough, Cr David Benson-Pope said. Insisting the meeting stayed under wraps meant the public were being kept in the dark.
''I think that the behaviour of the Justice Ministry around that matter, as well as other things, is completely over the top.''
Because Ms Adams had already announced the draft business case showed a $15million strengthening price-tag, there was no need for commercial sensitivities, he said.
''How many secrets can there be when they've already bandied the [$15million] figure around?
''I think there's a pattern of obstruction against people who are genuinely interested. And I'm very concerned by that.''
An open government should be operating ''the opposite'' to that, he said.
''There are far too many unanswered questions. When you run into a brick wall at every point, then you have to be very suspicious about that.''
Cr Benson-Pope said while details of last week's meeting were secret, he was able to confirm the engineers representing the Ministry of Justice included New Zealand-wide architecture and engineering firm Stephenson and Turner, and global engineering firm Aurecon.
''The telling thing of that is, the choice of big off-shore-connected transnational consultants is an indicator of the mindset of the ministry.''
It showed the ministry was willing to go to great lengths to find certain engineering opinions, while steadfastly refusing to listen to Dunedin engineers, he said.
And last week's meeting had done nothing to address whether the public's concerns about the $15 million strengthening plan were valid, he said.
''What has happened as a result of the restraining document is the people who might have been able to tell us that have been gagged.
''We're no further along in terms of what we've always argued, around doing it for the best price possible.
''[Dunedin people] are really hot about this. They're really frustrated that Dunedin's being ignored.''
Mr Woodhouse told the Otago Daily Times earlier this week Ms Adams had ''a number of priorities'' she needed to balance while deliberating on the building's fate, including financial practicalities.
Cr Benson-Pope said every government minister needed to be aware of financial practicalities, but in the case of the courthouse saga those practicalities had included spending $6.8million fitting out the city's rent-a-court facilities, spending about $600,000 every year on renting those facilities, and ignoring an earlier engineering report that suggested the historic courthouse could be strengthened for $2.5million without services having to relocate.
''None of it makes sense. I just think it's a worrying cop-out, because there are a lot more issues in terms of the provision of justice and the protection of the heritage industry in Dunedin.''
Ms Adams was sought for comment yesterday but chose not to respond. Dunedin Mayor Dave Cull will this week send a letter to Justice Minister Amy Adams and Prime Minister John Key, asking for confirmation the courthouse business plan would indeed go before Cabinet before year's end.
Cabinet's final meeting of the year is on Monday, December 7.
