Beatrix von Storch from the AfD said her party’s recent successes in the polls prove there is a change toward nationalist politics happening in Germany.
The right-wing national party, which was founded in 2013 as an anti-euro movement, has turned its focus to immigration and Islam in the wake of the Chancellor’s open door policy to refugees and migrants.
The AfD now has MPs in nine of Germany’s 16 state parliaments and is aiming to win its first national seats in next year’s federal elections.
Its success has been built on growing fears from citizens after Mrs Merkel took in some 1.1 million refugee and migrants in 2015 coupled with several high-profile terrorist attacks this summer.
The AfD deputy believes the results of Sunday’s regional vote could spell the end for the German Chancellor.
She told BBC Newsnight: “What we say is: this is the beginning of the end of Angela Merkel.
“We just came in second in the state where Angela Merkel comes from – it’s her home place where we won.
“We don’t have the majority of the votes yet but what we see, of course, is politics is shifting at least into our direction that even CDU and CSU are making more and more points that we have in our programme already because they see people want to have the politics taken in another direction.”
A Member of European Parliament, Ms Von Storch claimed her party was aiming to alleviate fears many Germans now had to live with.
She added: “The German society has a specific problem.
“Our claim that Islam does not belong to Germany is supported by something like 32-35% of German people, so this is not something that is only in our mind.
“People are voting for us because we have that line very clear.”