Wesfarmers Ltd (ASX: WES) reported on Tuesday that coal production on its Premier mine site near Collie in Western Australia suffered an output decline of 7.6 percent in the June quarter.

The company attributed the slide to a much lower demand coming from the state's electricity producer Verve Energy, which tapped Wesfarmers in July for an exclusive coal supply deal following the entry of a competing coal miner, Griffin Coal, into administration in January.

However, Wesfarmers said that its Curragh mine site in Queensland's Bower Basin saw a production spike of 6.4 percent in June as compared from the March quarter even as continuous rain and force majeure occurrences actually affected the site's output.

The company noted that its Curragh mine site is currently undergoing expansion works and targeted completion date is by the latter part of 2011.

On the other hand, production in Wesfarmers' Bengalla exploration sites in the Hunter Valley of New South Wales went up by 20.4 percent in the June quarter as against from prior quarter's figures thanks to the company's current operation on the site's more productive mine sequence.

And as of 1226 AEST on Tuesday, Wesfarmers shares were trading at $30.30, improving by 22 cents from the previous trading day.