Germany rebuked Secretary of State Marco Rubio after he slammed the country’s intelligence agency for classifying the far-right political party Alternative for Germany a “proven-right wing extremist organization.

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.

Until now, only AfD's regional branches in Thuringia, Saxony, and Saxony-Anhalt held that status, while the national party had been under observation as a suspected extremist group.