European Central Bank president Draghi, at the centre of the debt storm stalking the recession-hit single currency for the last three years, stands accused of breaching European Union statutes governing "impartiality, independence and objectivity".

The complaint was brought by anti-lobbying NGO Corporate Europe Observatory and a probe was opened on July 24, the EU Ombudsman's office said on its website. The campaigners say Draghi should resign.

The complaint argues that the ECB chief's place in the "Group of 30", which describes itself on its website as a "nonprofit, international body" gathering figures from private and public sectors and academia, "is incompatible with the independence, reputation and integrity of the ECB".

"No investigation has been launched," Gundi Gadesman, spokeswoman for the ombudsman Nikiforos Diamantoros, told AFP on Tuesday, rejecting "dramatisation" two days before a crunch ECB meeting at which the central bank is under pressure to do more to help Spain.

"We have transmitted the complaint to the ECB," Gadesman said, adding that the ombudsman would offer "recommendations" after studying responses, but that these are "not binding".

"We do not have the power to impose sanctions," she underlined.

Group of 30 members are high-flying private and public bankers such as JPMorgan Chase International chairman Jacob Frenkel or former US Federal Reserve head Paul Volcker, and include Draghi's predecessor at the ECB, Jean-Claude Juncker.