Gold recently hit more than $2000 an ounce and market analysts predict it may go up further because of the impact of the Covid-19 pandemic, The National newspaper reports.
Namah blamed the government for "this loss of revenue" because of its refusal to extend the special mining lease to operator Barrick Niugini after it expired last year.
The company is challenging the government's decision in court.
"In addition to the loss in potential revenue for the mine from the surge in gold price, the nation is missing out on hundreds of millions of kina in taxation," Namah said.
"The Enga provincial government is (also) losing tens of millions of kina in contributions from the mine."
He said the Porgera mine community was also missing out on business activities and amenities such as electricity, transport and health services.
He added that 2650 Porgera employees have been laid off.