The European Commission said it will seek "clarifications" from its former president, Jose Manuel Barroso, about his controversial job at US investment bank Goldman Sachs.
The current president of the commission, Jean-Claude Juncker, has launched an unprecedented probe into whether his predecessor's new post conforms to EU ethical standards.
Barroso who headed the EU executive for a decade until 2014 caused an outcry when he joined the US bank in July on an undisclosed salary, 20 months after leaving his European post which has an 18-month 'cooling off' period.
French President Francois Hollande called Barroso's appointment "morally unacceptable", saying Goldman Sachs was implicated in helping Greece to hide the size of its debts in 2001, a key factor in the run up to the eurozone crisis.
Part of the role the former prime minister of Portugal will perform for the bank as a non-executive chairman will be to advise it about Brexit.
Barroso's appointment led to 140,000 respondents signing a petition calling for him to forfeit his EU pension, while EU ombudsman Emily O'Reilly has also raised concerns about the move.
Juncker declared a three-person ethical committee will study whether Barroso's new appointment conforms to EU ethical standards.
He added in a letter that Barroso will be asked "to provide clarifications on his new responsibilities and the terms of reference of his contacts, on which I will seek the advice of the ad hoc ethical committee".
Juncker pointed to a treaty article called 245 TFEU in his letter, which says former commissioners have a "duty to behave with integrity and discretion as regards the acceptance, after they have ceased to hold office, of certain appointments or benefits".
If a breach of that ethical code is proven, the Commission can deprive a former commissioner of his or her EU pension.
The EC president also added that Barroso will be stripped of his VIP former president status when on business at the EU, and will instead be treated a common "interest representative".
O'Reilly said she was "pleased to see that President Juncker has responded to the widespread concerns about this appointment".