Poland's parliament took one of its first steps towards opening up its natural gas market, passing a bill late on Friday that allows potential rivals to keep required reserves anywhere in the European Union.

The new law, which will come into effect after 30 days, aims at liberalising gas storage regulations, which at the moment effectively ensure a dominant position for PGNiG .

Until now, companies willing to enter the 14-billion-cubic-metre (bcm) gas market could only keep obligatory reserves in Poland, where PGNiG controls all the storage capacity.

Any company that wants to trade larger volumes of gas on the Polish market currently has to either build its own storage facilities or rent them from the monopoly, which has been reluctant to grant access to its facilities.

The bill, which had stumbled in the parliament before being passed in the last sitting ahead the October election, also doubles the amount of gas a company can sell before it must hold gas reserves to 100 million cubic metres annually.

"By liberalising this requirement, we are making easier for firms to start operations on the Polish market," said Economy Minister Waldemar Pawlak.

Natural gas prices in Poland, which meets much of its needs with imports from Russia, are set by URE and are often below import prices.

The European Commission in April gave Poland two months to drop this system of setting tariffs, which effectively blocks competition to PGNiG, or said it would sue the country in the European Court of Justice.