U.S. Ambassador to Germany Richard Grenell, left, and German President Frank-Walter Steinmeier | Odd Andersen/AFP via Getty Images German politicians call on US to withdraw ambassador Richard Grenell under fire for saying he’ll seek to ’empower’ anti-establishment parties across Europe.

German politicians are calling for U.S. Ambassador to Germany Richard Grenell to be recalled, following a controversial interview in which the diplomat claims he is seeking to boost anti-establishment parties across Europe.

"What this man is doing is unprecedented in international diplomacy," former Social Democrat leader Martin Schulz told German daily Tagesschau on Tuesday.

"If a German ambassador in Washington said, 'I'm here to strengthen the Democratic Party,' he would be thrown out immediately," he added.

Schulz accused Grenell of acting as a representative of a political movement instead of maintaining a neutral stance toward his host country, and on Monday described him as a "far-right colonial official."

In an interview published late Sunday, Grenell told far-right news site Breitbart he "absolutely wants to empower other conservatives throughout Europe" and encourage people to rise up against "elites."

Grenell, who took office less than a month ago, has been asked to clarify his comments during his inaugural visit to the foreign office on Wednesday, according to Tagesschau.

Sahra Wagenknecht, the leader of Germany's left-wing Die Linke, has also called for Grenell to be withdrawn.

"If the German government takes our country's democratic sovereignty seriously, it should not invite Grenell to coffee, but expel him immediately," Wagenknecht said.

Jürgen Hardt, the foreign policy spokesperson for Angela Merkel's conservative bloc, responded to the comments by saying: "It is not my place to tell the new U.S. ambassador how to exercise his functions or which media outlets to speak to."

He added that he hoped Grenell would "invest all of his energy into supporting close coordination" on a number of urgent transatlantic issues, including the Middle East and trade policy.

"The idea that I’d endorse candidates/parties is ridiculous," Grenell tweeted in response to the blowback over his comments. "I stand by my comments that we are experiencing an awakening from the silent majority — those who reject the elites & their bubble. Led by Trump."

Grenell is due to host Austrian Chancellor Sebastian Kurz — a staunch critic of Angela Merkel's migration policy whom Grenell called a "rockstar" of European politics in his Breitbart interview — for a meal on June 13, German media reported.