E.ON Chief Executive Johannes Teyssen told shareholders on Wednesday that no decision had been made over how E.ON would vote at Uniper's annual general meeting in relation to a motion to appoint a special auditor.

Uniper had said on Tuesday that Cornwall Luxembourg S.a.r.l., which it said was backed by activist investor Elliott, had made such a proposal to identify possible breaches of duty by the board in relation to Fortum's bid.

Fortum, which is currently awaiting regulatory approval to buy a 46.65 percent stake in Uniper from E.ON, in late April said that Uniper had actively worked against the proposed transaction in Russia.

E.ON, which will likely still own the stake at Uniper's shareholder meeting scheduled for June 6, will listen to all sides before deciding whether or not to support the motion, Teyssen said at the group's annual shareholder meeting.

"It is still a few weeks until June 6 and then we'll see. But again, this is nothing that causes us to be overly concerned," he said.

(Reporting by Tom Kaeckenhoff; Writing by Christoph Steitz; Editing by Arno Schuetze)