Babiš and his ANO party won the most seats in parliament in elections last October but lacked a majority. He has run a caretaker administration since their minority government lost a no-confidence vote in January.

Other parties shunned ANO because Babiš faced criminal charges dating back a decade. He denies the charges.

President Miloš Zeman is due to appoint Babiš prime minister again on Wednesday, after Babis reached an agreement on a coalition with the Czech Social Democratic Party (ČSSD). The agreement is now subject to a referendum among ČSSD members. The result is expected in mid-June.

The two parties will only have 93 votes combined in the 200-seat lower chamber of parliament, so they will still need to lean on the Communist party for support.

The prospect of Communists, who ran Czechoslovakia’s Soviet-era dictatorship before 1989, getting a share of power again sparked Tuesday’s protests.

The largest crowd assembled in Wenceslas Square in downtown Prague, where people listened to speeches and songs criticising and mocking Babiš over his past as a Communist party member.

“I don’t care about politics at all really, but now I feel that it is necessary for the future of my children to go to the streets,” Václav Bozděch, 56, said at the protest in Prague.