Hungarian Prime Minister Viktor Orban took it as a joke but his supporters at home were furious when European Commission President Jean-Claude Juncker saluted him with an audible "Hello dictator" before the world's cameras last month.

The unorthodox greeting at a summit with the European Union's eastern partners in Riga on May 22 was one of those rare moments when the underside of politics appears fleetingly on the surface. Banter aside, the EU authorities have proved largely ineffective in curbing the conservative nationalist Orban's drive to tighten his grip on the central European state.

"Juncker has Orban on his watch list," says an aide to the head of the EU executive, which is in charge of upholding the bloc's treaties, including civil rights.