EU ombudsman calls for independent watchdog on 'revolving doors'

She warned that "there may be a case for taking the assessment of conflicts outside the institutions, and to set up an independent body to decide on conflict of interest ... if they [the Commission] won't impose sanctions."

"If badly handled by the EU institutions [the period] could lead to reputational damage and legal challenges," O'Reilly said, adding that "it makes sound business sense for the EU to avoid all pitfalls from 'revolving doors'".

Under the current regime, the commission itself decides on whether appointments could lead to a conflict of interest, based on its own staff regulations.

The commission also has a three-member ethics committee monitoring departing commissioners who are looking for new jobs.

Setting up an independent watchdog would require the agreement of the EU institutions.

But NGOs and transparency watchdogs say former commission staff are often fast-tracked into powerful consultancy firms and then lobby people they had previously worked with while at the EU institution.

The question of conflicts of interests is also high on the commission's radar following the departure in 2012 of the health and consumer protection commissioner, John Dalli, over his alleged involvement in a tobacco bribery scandal.

Commenting on her investigation, O'Reilly said that "the commission certainly recognises that there is a problem but the question is whether these structures are effective ... it strikes me that there is an issue to implement and a reluctance to impose sanctions."

A number of commissioners and a large number of their handpicked personal cabinet members will enter the job market when the EU executive's current term ends in September.

In February, O'Reilly launched an investigation into ten cases where the commission had allegedly failed to prevent conflicts of interest.

The investigation required the commission to disclose all revolving door cases for the past three-years. NGOs and transparency campaigners argue that existing EU staff regulations and rules are too weak or poorly implemented.

O'Reilly, who said that she had posed a series of questions to the commission, including mooting the possibility of a central register for assessments of possible appointments, added that her investigation would assess whether the commission faced "a systemic problem".

Meanwhile, MEPs on the European Parliament's constitutional affairs committee also backed plans on Tuesday to force lobbyists working in and around the institutions to sign the EU's "transparency register".

So far an estimated 75 percent of all relevant business-related lobby groups and approximately 60 percent of NGOs operating in Brussels have signed the register, which is currently voluntary.