* Commission seeking to enforce single energy market
* Polish infringement case dates back to June 2009
BRUSSELS, June 20 (Reuters) - The European Commission has referred Poland to the EU Court of Justice, saying its regulated gas prices for business consumers are in breach of EU rules.
The Commission, the EU executive, has stepped up action to enforce its single energy market, which aims to increase consumer choice, improve security of supply by increasing cross-border energy flows and make energy prices more competitive.
"Competitive energy markets will offer citizens and businesses secure and sustainable energy supplies at lowest possible cost," EU Energy Commissioner Guenther Oettinger said in a statement on Thursday.
The Commission says regulated prices can limit competition and distort markets because they do not reflect demand.
The case dates back to June 2009, when the Commission opened an infringement procedure against Poland, which still is not complying despite numerous exchanges, it said.
Poland could face heavy daily fines, depending on the EU court's decision. (Reporting by Barbara Lewis; editing by Jane Baird)