The designation is certain to inflame debates over whether the party should be banned, though some polls show it to be the most popular in the country.

The reclassification — AfD was previously designated a “suspected” extremist group — is likely to reignite debate over a political ban on the party.

Germany's domestic security agency classified the Alternative for Germany (AfD) as "extremist" on Friday, allowing for closer monitoring of the country's largest opposition party, which condemned the move as a "blow against democracy".