Senior Czech judges on July 21 denounced Poland's judicial overhaul as an attack on the rule of law.

With big street protests in the Czech Republic's neighbour seemingly gathering momentum – 120 were planned for locations across Poland on July 22 – the Czech judiciary released a statement reading: "While keeping in mind and respecting the sovereignty of the Polish state, we can not stay silent about the steps that threaten its very source, which is the untouchable values of European civilisation, humanism and fundamental rights and freedoms."

It was signed by the heads of the constitutional court, supreme court and supreme administrative court, and also the top state prosecutor and Czech ombudsman.

The lower house of the Polish parliament on July 20 passed a hugely controversial law that effectively places Poland's supreme court under the control of the ruling right-wing populist and national conservative Law and Justice (PiS) party, removing checks and balances usually expected of a modern democracy. The upper house approved the legislation the next day, meaning only President Andrzej Duda's signature is needed to make it law. Also presented to him for final approval is a bill that would award government-appointed members of the National Council of the Judiciary near-veto rights over all judicial candidates.

The European Commission has said it could move to invoke Article 7 of the Treaty on the European Union against Poland should the president sign the legislation that undercuts the separation of powers between the legislature, executive and judiciary. The article, never before used against a member state of the European bloc, can lead to the removal of a country's EU voting rights.

However, Hungary, governed by the populist and illiberal national conservative Fidesz party, is likely to move to veto such a move against Poland.

With Slovakia governed by the populist and at least nominally left-wing Smer-SD party, it is only the Czech Republic, of the Visegrad Four in Central Europe, that has not gone over to populism. But that could well change in the general election planned for October.