The European Commission had asked national parliaments to test subsidiarity and the committee found it violates the principle, committee chair Jožef Horvat told the STA.

The tight 8-7 vote came despite the plan having received the green light from the Justice Committee, which endorsed the idea despite some reservations.

The principle of subsidiarity, enshrined in the EU treaties, requires that decisions are taken at the lowest possible level.

Horvat said the committee vote was tantamount to a "yellow card" for the European Commission, which will now have to launch new deliberations or withdraw the plan.

The Slovenian government formally supports the idea, but the Justice Ministry has expressed reservations about the hierarchy.

State Prosecutor General Zvonko Fišer told the Justice Committee in mid-October that the country was right to have reservations regarding the structure of the new office.

He said a debate was under way among European prosecution services on what would be the best structure of the new office.