The Covid-19 pandemic has led to a surge in authoritarian behaviour by governments, posing a growing threat to democracy, hundreds of former prime ministers, presidents, Nobel laureates and lawmakers have warned.

The virus has prompted countries across Europe, Asia, the Americas and Africa to step in, many limiting free movement, free speech, public assembly and other civic rights.

“Authoritarian regimes, not surprisingly, are using the crisis to silence critics and tighten their political grip,” wrote some 500 signatories, including more than 60 former leaders, in an open letter organised by the Stockholm-based Institute for Democracy and Electoral Assistance (Idea)...