If the Nord Stream 2 gas pipeline will be built, it must fully comply with European Union rules, like any other infrastructure project subject to European laws concerning the environment, economy and government procurements, European Commission Vice President in charge of Energy Union Maros Sefcovic said.

EU legislation also applies to "offshore infrastructure under the jurisdiction of members states [of the EU] including their exclusive economic zone," and the "construction of such an important infrastructure project as Nord Stream 2 cannot happen in legal void," Sefcovic said on Wednesday at a conference in the European Parliament called Nord Stream 2 - Energy Union at the Crossroads.

"This would also run counter to the interest of economic operators in having legal certainty. Neither can it be exclusively operated only according to Russian law. Against the background of colliding legal regimes, Nord Stream 2, if built, has to be operated under a legal framework which also takes duly account of the key principles of our energy market rules," Sefcovic said.

He said all energy infrastructure "can face disruption, or even catastrophic interruption." He said Germany has "exemplary rules" for the operation of pipelines connected to Norway, adding that there are other examples of agreements, such as between Russia and Poland.

"We will urge the Member States to clarify issues of environmental liability; in this context, the Commission is currently reviewing the situation at all sub-sea entry points into the EU, and will assess what further action may be needed," Sefcovic said.

The onshore section of Nord Stream 2, whatever its route on EU territory, must respect the rules of the Third Energy Package and "the Commission will ensure their correct application," he said.

The impact of the Nord Stream 2 project goes clearly beyond the legal discussions," Sefcovic said. "Nord Stream 2 could alter the landscape of the EU's gas market while not giving access to a new source of supply or a new supplier, and further increasing excess capacity from Russia to the EU," he said, adding that this "raises concerns."

The "EU will only financially support infrastructure projects that are in line with the core principles of the Energy Union, including the EU Energy Security Strategy. Diversification of energy sources, suppliers and routes is crucial for ensuring secure and resilient supplies to European citizens and companies. Nord Stream 2, as presented so far, does not meet these conditions," Sefcovic said.

No market operator should be allowed to have a dominant position over consumers, he said. This is the context in which Nord Stream 2 should be considered, and this concern has been expressed in a recent letter from nine prime ministers to EC President Jean-Claude Juncker, Sefcovic said.

"The concerns are of various nature, be it legal, geopolitical or economic," Sefcovic said.