Viktor Orbán, Hungary’s prime minister, says “Brexit is a fantastic opportunity . . . There is a possibility of a cultural counter-revolution now” Darko Vojinovic/ AP

Former communist states are planning to exploit the fallout of Brexit with a “counter-revolution” designed to block migrant deals and assert the power of national governments over Brussels.

Hungary, Poland, the Czech Republic and Slovakia, an influential diplomatic European Union bloc known as the Visegrad Group, will lobby together at a summit next week to ensure that national governments are put back in the EU’s driving seat.

The summit will gather all EU leaders, excluding Theresa May, in Slovakia’s capital to forge a new vision of Europe. It is expected to expose the rift between newer member states in the east and western countries committed to a European project based on open borders and markets.

Viktor Orbán, Hungary’s populist conservative prime minister, pledged to use…