BERLIN (Reuters) - A German state premier was elected with the support of the nationalist Alternative for Germany (AfD) and Chancellor Angela Merkel’s conservatives on Wednesday, shattering the post-war consensus among established parties of shunning the far right.

German Chancellor Angela Merkel arrives for the weekly cabinet meeting at the Chancellery in Berlin, Germany, February 5, 2020. REUTERS/Annegret Hilse

Thomas Kemmerich, a little-known liberal Free Democrat (FDP), became the first state premier elected with the support of the AfD, with whom Merkel’s conservative Christian Democrats (CDU) sided to the disgust of her national coalition partners.

The CDU and all the other established parties have previously ostracized the AfD over what they say are racist views held by some of its members.

Merkel’s Social Democrat (SPD) national coalition allies accused her CDU of backtracking on a pledge never to cooperate with a far-right party. The CDU rejected the accusation, saying it was not responsible for how AfD lawmakers voted. Wednesday’s ballot was secret.

“The events in Thuringia break a taboo in the history of political democracy in the Federal Republic,” SPD Finance Minister Olaf Scholz tweeted. “Very serious questions arise for us with the CDU’s federal leadership.”

CDU leader Annegret Kramp-Karrenbauer said her party’s national leadership opposed both cooperating with the AfD and joining a Kemmerich-led state cabinet. “The best thing would be for voters in Thuringia to have new elections,” she added.

The SPD is unlikely to ditch Merkel’s national coalition over the vote in Thuringia but the center-left party said its supporters would hold a protest outside the CDU headquarters in Berlin.

“The vote on the new premier minister in the state of Thuringia marks a new milestone in German politics and bears the potential of more shockwaves in national politics,” said ING economist Carsten Brzeski.

Kemmerich won 45-44 against Bodo Ramelow, the outgoing premier of The Left party. Ramelow’s leftist coalition failed to secure a majority in an October regional election.

Kemmerich, whose FDP is the smallest party in the regional assembly, said he would launch talks with the CDU, SPD and Greens on forming a government.

SPD national leader Norbert Walter-Borjans spoke of an “unforgivable dam burst, triggered by the CDU and FDP”.