Poland's Treasury Ministry said recently the Warsaw bourse had until the end of 2011 for exclusive talks to buy the stake.

The ministry declined to comment, while the bourse was not available for comment.

Polish media said Scandinavian power exchange Nord Pool Spot, Dutch exchange APX-Endex and Polish grid company PSE-Operator were also invited to bid.

The Warsaw bourse launched its energy trading platform last year, but due to legal issues trading never took off.

Traders and analysts believe the region's energy trading market is bound for consolidation as it is not sufficiently liquid to support so many small players.