Former EU chief Donald Tusk is urging the largest party in the European Parliament to expel Viktor Orban's Fidesz from its ranks.
Tusk made the plea to the European People's Party (EPP) after Hungarian MPs passed a controversial coronavirus law.
It allows Hungarian PM Orban — long at odds with Brussels — to rule by decree as long as a state of emergency is in effect.
The law also sets prison terms of up to five years for those convicted of spreading false information about the pandemic.
EPP president Tusk, in a letter to members, accused Orban of "making use of the pandemic to build a state of permanent emergency", something he said was "morally unacceptable".
The EPP — the European Parliament’s largest and most influential group — has been divided over how to act in the face of persistent breach of EU principles over several years.
The party suspended Fidesz in the run-up to the European Parliament elections last year after a row over anti-EU posters.
Orban has been widely accused of using the virus to further dismantle democratic mechanisms in Hungary.
The European Commission is set to discuss Hungary's emergency law later today.