Hungary's six largest opposition parties pledged Thursday to form an unprecedented wide-ranging alliance to challenge Prime Minister Viktor Orban at the next general election in 2022.

Opposition parties accuse the nationalist Orban of steering Hungary toward authoritarianism and away from mainstream democratic and European Union values.

The self-styled "illiberal" premier has regularly clashed with the EU over alleged backsliding on rule-of-law, migration, and human rights issues.

Orban has won three consecutive landslides since 2010, partly due to election rule changes he oversaw.

But with around half of the electorate voting for opposition parties Orban would be vulnerable to a unified front.

Hungary's Prime Minister Viktor Orban (pictured July 2020) has won three consecutive landslides since 2010, partly due to election rule changes he oversaw
Hungary's Prime Minister Viktor Orban (pictured July 2020) has won three consecutive landslides since 2010, partly due to election rule changes he oversaw POOL / JOHN THYS

The new alliance, which includes usually bickering leftist, liberal and right-wing parties, said in a joint statement that it had "heard the will of their voters".

It has agreed to create a common programme for government and stand single candidates against Orban's powerful Fidesz party in all 106 electoral districts, it said.

If parties failed to agree on the best candidate during talks then preliminary run-offs could be held.

The opposition's new strategy was partially applied at municipality elections last October and helped deliver it shock wins in Budapest and several regional cities.

If the alliance won in 2022 the parties pledged to govern together "in the interests of Hungary on the basis of an agreed programme and principles," said the statement.