The trip has sparked claims that the official’s acceptance of the offer to travel by such means to Budapest for a conference may have constituted a conflict of interest in his role as Commissioner.
The offer was made by a businessman said to have close links to the Kremlin.
Speaking in Strasbourg on Tuesday, the leader of the Socialist group in Parliament, Gianni Pittella said that in accepting the invitation the Commissioner had “made a mistake.”
The Italian MEP also said there should be a full parliamentary hearing into Oettinger’s recently announced change of portfolio.
Oettinger is to replace Kristalina Georgieva as the European budget Commissioner after she resigned to move to become CEO of the World Bank.
Oettinger is presently the Commissioner for digital economy and society and previously served as the state premier of Baden-Württemberg until 2010, after which he moved to the Commission.
A former energy Commissioner, Oettinger is due to take up his latest role with the Commission in January. He could also take over Kristalina Georgieva’s vice-presidency role when she leaves.
Last week, Parliament’s President Martin Schulz is thought to have proposed bypassing the hearing process that Commissioners usually have to undergo.
Oettinger, a German national, would instead be subject to an exchange of views with MEPs before becoming the new budget Commissioner.
But, speaking at a news conference in parliament, Pittella raised new concerns about Oettinger’s trip to Budapest with a lobbyist. Oettinger was also in the news recently after he made allegedly offensive remarks about the Chinese for which he later had to apologise.
Pittella said, “When it comes to taking flights on private planes, Commissioners have to be particularly cautious.
“He seems to be making one gaffe after another and we have repeatedly asked for clarification (about the Budapest trip). What he did was a mistake and we disagree with it.
“We believe that he should now be subject to a formal confirmation hearing before he takes up the budget post.”
It would be an opportunity, he said, to question Oettinger on the recent statements and actions he has made.
Pittella said, “A hearing would give us the chance to evaluate his abilities and competences for this new role. I would imagine that would be a very difficult hearing for him.”
Speaking separately, Syed Kamall, Chair of Parliament’s ECR group, described the Commissioner as “a gaffe-prone, untouchable German man”.
Kamall said, “You’ve got to ask how many times Oettinger is going to get away with this behaviour.”