Brussels is probing Ireland, Luxembourg and the Netherlands over their tax deals with multinationals paving the way potentially for a formal investigation into illegal sweeteners.
Europe's top competition authority has asked the governments to explain their system of tax rulings and give details of assurances given to several specific companies – including Apple and Starbucks – according to people who have seen the request.
(Read more: EU lawyers say transaction tax plan is illegal)
The move threatens to open a new front in the global clampdown on tax evasion through enforcing the EU's state aid rules – a unique regime that bans serious distortions of competition through tax breaks to favoured private groups.
This request, sent to at least three EU countries, represents the opening step of an informal probe and does not mean the European Commission has identified wrongdoing. But even this preliminary move has rattled officials in some of the capitals targeted.