The Papua New Guinea opposition is promising legal action to try and overturn the government's acquisition of all the shares in the Ok Tedi mine.
Last month the government, with near unanimous support, absorbed the 63 percent of shares it did not already hold.
These belonged to the Sustainable Development Programme, which was established primarily for the people of Western Province where Ok Tedi is located.
But the Post Courier reports the opposition leader Belden Namah saying the actions of the government are undemocratic.
He says it has taken a dictatorial approach.
Mr Namah says he believes the government may offer the shares to investors of its choice or use the asset to secure overseas loans.
He says he has assured the landowners the opposition would take the issue up in court.