Germany's far-right AfD party has been criticised for launching a child informant programme in schools where pupils expose teachers who attack the party or show political bias.

The Hamburg chapter of Alternative Fur Deutschland, which made major gains in last year's general election, launched a "Neutral Schools" website for anonymous complaints about teachers.

But Katarina Barley, the German justice minister, condemned the programme, warning that "organised denunciation is a tool of dictatorships."

"A party using this to expose disagreeable teachers ... reveals a lot about its own understanding of democracy," she added.

German teaching unions also hit out at the Stasi-esque surveillance scheme, which the AfD hopes to extend to nine other states, including Bavaria, Brandenburg, Baden-Württemberg and Saxony.

"It's to be expected that a party that wants to ostracise dissenters is now creating platforms to denounce people who have different opinions," Ilka Hoffmann, a board member of the German Education Union, told the Funke newspaper group.

"Teachers should be scared. This is a frightening development."

The AfD is the largest opposition party in the German parliament, the Bundestag, following a surge in support in the September 2017 election which handed them 90 seats.

It has capitalised on popular anger against Chancellor Angela Merkel's liberal refugee policy that resulted in a record refugee influx in 2015.