Philip Lowe, the head of the Commission's directorate-general for energy, said the EU's 27 member states have opposed proposals to grant Brussels more powers to supervise energy deals with foreign countries.
The Commission proposed new rules earlier this month that would force EU states to share the details of planned energy accords in advance with Brussels and give the EU executive the power to negotiate some energy deals on behalf of governments.
Analysts have interpreted the plan as an attempt to prevent cosy bilateral ties between big gas consumers, such as Germany and Italy, and the EU's main supplier Russia.
"Without exception, all smaller member states strongly backed the direction of the paper," Lowe said after the 27 member states had set out their positions on the proposals earlier this week at an informal meeting of energy ministers in Poland.
"Without exception, all the major member states said 'well, we might be prepared to look at it on a case-by-case basis if there is some justification, but in other cases bilateral agreements are a national issue'," Lowe told an EU energy policy seminar held by the Brussels-based think-tank Bruegel.
Lowe said bigger EU governments had agreed on the need to ensure energy deals are in line with the bloc's internal energy market rules – but they were against revealing the details of such deals in advance, as proposed by the Commission.
"You don't need to be Einstein to work out what that all leads to: a mess. A mess for investors and a mess legally," Lowe said.
EurActiv with Reuters