WILLIAMS LAKE, B.C. - A federal panel weighing the future of a previously rejected gold and copper mine in British Columbia says the company has not provided sufficient information to proceed with the new environmental assessment.

The Canadian Environmental Assessment Agency panel wrote to Taseko Mines Limited this week, requesting additional information on the cumulative effects of the proposed open-pit mine to be located approximately 125 kilometres southwest of Williams Lake, B.C.

The company responded the next day with a letter expressing frustration with the request.

"It is discouraging that the panel has used an apparent technicality to stop the timeline remaining for the panel to complete its review," wrote John McManus, senior vice-president of operations.

"Taseko does not agree that there is a deficiency in the (environmental impact statement) related to the approach that was used to assess the cumulative environmental effects which would cause the panel to determine that the EIS is not sufficient to proceed to panel hearings."

The original application for the $1.1-billion New Prosperity project received provincial approval but was rejected by a federal panel in 2010.

Taseko (TSX: TKO) resubmitted the environmental impact statement in September. The panel rejected an earlier draft submission, saying it lacked information.

Taseko's revised plan and resubmitted application included an additional $300 million in costs in order to save Fish Lake, a water body culturally significant to local First Nations that the original proposal would have drained to use as a tailings pond.

Taseko said the original assessment found that there were no significant adverse effects on vegetation, deer, moose and other wildlife or surface and groundwater. Therefore, there is no need for this panel to revisit those issues, the company said.

The first panel found only grizzly bears and fish and fish habitat could suffer cumulative adverse effects, Taseko wrote, so only those issues need to be addressed.

The panel responded Thursday.

"The panel disagrees, and finds Taseko's cumulative effects assessment methodology and, accordingly, the (environmental impact statement) deficient," said the letter to McManus signed by panel chairman Bill Ross.

Ross said the panel is not bound by the findings of the previous panel.

"Taseko narrowed the scope of its cumulative effects assessment in a manner that is inconsistent with the (environmental impact statement) guidelines and the act," he wrote, reiterating the request for additional information.

Several area First Nations oppose the mine, which they claim will affect fish and wildlife outside well beyond Fish Lake.

The panel's final report to the minister is expected within 235 days after the company submits the final environmental impact statement.

In October, the Vancouver-based mining company reported a third-quarter loss of $3.9 million, compared to a profit of $30 million for the same quarter of 2011.