The European Union's executive body is formally asking 18 member countries to implement rules aimed at liberalizing the EU energy markets adopted years ago, as part of a bid to speed up reforms and meet a 2014 deadline, the European Commissioner for Energy said Thursday.

"More than six months after the deadline, the majority of member states have still not adopted the national legislation to transpose the Third energy package into their national legislation," Guenther Oettinger said in a speech Thursday, referring to the latest package of legislation agreed by EU governments.

"Such delays seriously risk undermining our common [EU] objective of completing the internal market within three years," Oettinger said.

The commission is opening an infringement procedure against 17 countries in the field of electricity and 18 in the field of gas. This means it is sending a formal letter to demand that the countries speed up the transposal of the EU rules into their national legal systems, while asking why it is taking longer that expected.

France and the U.K. are among the bigger economies in the EU that the commission is targeting, together with Spain . Germany , Italy , Poland and Latvia weren't in the list.

Liberalizing the national gas and electricity markets, making them more competitive and favoring their interconnection is a top priority for the EU, and the commission has used all its powers--taking countries to court and opening antitrust investigations--to reach its objective.

However, that has created tensions with Russia , upon which many member countries heavily depend for their gas supplies.

The commission wants to make sure that big energy companies that produce gas and electricity don't also own the network to distribute them, so that competitors can more easily use those infrastructures if interested.

This effort should encourage cross-border investment, boosting interconnections among countries, which would lead to more security for the supply of energy, as gas and electricity would be able to move freely across borders.

This would reduce the risk that a cut in gas or electricity from outside the EU critically crippled a country's supply, as it happened in 2009, when a price dispute between Russia and Ukraine triggered a stoppage of gas flows to eastern Europe for weeks.

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