German Chancellor Angela Merkel on Thursday voiced full backing for European Commission chief Jean-Claude Juncker in a widening row with Hungary's hardline Prime Minister Viktor Orban.

The Hungarian government on Tuesday launched a new anti-immigration media campaign accusing Juncker and US philanthropist George Soros of allegedly supporting illegal migration.

"Jean-Claude Juncker has my full solidarity and we will make that clear too in our talks with Hungary," Merkel told journalists.

Orban's attacks against Juncker and EU institutions have prompted calls for his party to be thrown out of the centre-right EPP bloc which holds a majority in the European Parliament.

In particular, Manfred Weber of Merkel's Bavarian allies the CSU has come under pressure to act as he is leading the EPP's campaign in May's European elections.

Weber has thus far defended the EPP's decision to allow Orban's Fidesz to swell its ranks in the Strasbourg assembly.

But the Hungarian government's direct attack on Juncker's Commission has now upped the stakes.

Juncker had already said last year that Orban's party has no place in the EPP.

Orban's government, which has frequently clashed with the EU on migration, has regularly undertaken similar campaigns in the past, including "Let's Stop Brussels" and "Don't let Soros have the last laugh."

In recent years, Orban has blasted the Hungarian-born Soros, 88, as a "public enemy" for allegedly backing uncontrolled mass immigration.