Its controlling shareholder and managing director, George Kerr, has also been criticised for failing to show up at annual meetings.
"The situation has become farcical when a company that continually fails to meet its obligations is allowed to remain listed," said Shareholders Association chairman John Hawkins.
Guernsey-based PGC had its stock suspended from trading in October 2014 after the company missed the deadline for filing its annual report.
Trading resumed when the report was filed in November with a tag from former auditor PwC, which said it was unable to obtain sufficient information about the firm's investment in the Torchlight Fund, which has targeted distressed assets.
Hawkins said the association had made written complaints regarding PGC to the Financial Markets Authority (FMA) and NZX on five occasions since November.
"The FMA apparently requested some clarifications from PGC, but in our view could have done much more," Hawkins said. "However, NZSA believes that NZX has a responsibility to take the overall pattern of behaviour of its listings into account."
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An NZX spokeswoman said the association had not provided any information that indicated a failure by PGC to meet its continuous disclosure obligations.
"Under the listing rules, NZX has the ability to cancel an issuer's listing," she said. "With the information it currently has about PGC, NZX does not consider that current circumstances justify the exercise of that discretion."
The spokewoman said the accounting treatment of PGC's financial statements was a matter for the FMA.
"NZX and the FMA continue to engage with PGC as a matter of priority on a range of issues, including those raised by the NZSA, to ensure compliance with applicable financial reporting requirements and to ensure the market is adequately informed," she said.
"NZX does not intend to comment further on this matter."
An FMA spokesman said the regulator had engaged with PGC's directors and advisors on a number of issues including PGC's financial reporting, and would continue those discussions "where appropriate".
"We respect the NZSA views and have engaged with the NZSA on a number of occasions in respect of PGC."
Earlier, Hawkins said the general reaction to its complaints about PGC had been that the market was informed and could make its own decisions.
"In our opinion, this is total nonsense," he said. "Just because the market knows a company may not be in compliance does not mean that shareholders are able to assess the effect of that non-compliance without access to full, accurate and timely information."
Hawkins said shareholders, including those from the association, had sought clarification at last year's annual meeting, but Mogridge had "consistently refused" to answer questions about key operating investments.
The Herald is seeking comment from PGC chairman Bryan Mogridge.
"It is hard to see how PGC investors or potential investors are supposed to make informed judgements on anything relating to this company, much less the value of their shares," said Hawkins.
He said the association had asked the FMA and NZX to send representatives to the meeting to "observe the conduct", but neither organisation had done so.
Listing rules gave NZX the power to cancel PGC's listing, Hawkins said.
"In our view, it is time NZX stopped the constant appeasement and got on with their primary obligation to protect investors from a company that is repeatedly failing in its obligations."