The German news weekly was shaken this week with what the magazine branded "a low point in the 70-year history of Der Spiegel" after it was revealed that its award-winning journalist Claas Relotius had falsified numerous reports including those on US policies.

The management of the respected magazine Der Spiegel has fought off claims by US Ambassador to Germany Richard Grenell who accused the weekly of “institutional bias” towards his country, particularly after Donald Trump became US president, and even encouraging “anti-American” reporting. According to him, the number of Spiegel’s anti-American reports has increased. In his letter, addressed to Der Spiegel’s future editor-in-chief Steffen Klusmann, the American diplomat, voiced distress over the latest revelations about faked stories, which impacted US policies and part of the US population.

He also expressed hope that the matter would be thoroughly investigated by an independent third-party organisation and also insisted that the magazine’s internal processes should be reviewed.

“The most important question is yet how this blatant anti-Americanism could be published without an editor doubting the accuracy of reporting and how much damage had been caused over the 7 years of unverified reportages”, his letter, published by Spiegel reads.

Later that day, the current Spiegel editor-in-chief, who leaves his post on 31 December, responded apologising to all American citizens who have been insulted or vilified by the faked reports, saying the fact-checking system failed and promising to work on their standards.

READ MORE: Der Spiegel Exposes One of Its Top Reporters as ‘Fake Stories’ Creator

He refuted any allegations about the anti-American bias, stating that if they criticised the American president, it is not anti-Americanism, but criticism of the White House's policies.

“Anti-Americanism is deeply alien to me and I am fully aware of what Germany has to thank the US for: very much. There is no institutional bias against the US at Spiegel. You suggest that there have been other cases of incorrect reporting about your country. Please tell us about, we'll deal with them”, his letter reads.

The US envoy didn’t accept this explanation, lambasting it with a Twitter offensive. First, he posted a collage of Der Spiegel covers (many of them dating back to the George W. Bush-era, however).

​Then repeated his accusations of fabricating stories and lambasted critics of his crusade.

We value policy criticism. We love a free press. But @Spiegel literally fabricated stories saying people (Americans) were racist & xenophobic. They made up events, details, & lies — and no editor checked the stories. Every real journalist should be outraged by this. https://t.co/CVlSqgXIQe — Richard Grenell (@RichardGrenell) 22 декабря 2018 г.

Of course. But you changed the subject. We were talking about bias from journalists. Reporters who lie about their objectivity. Journalists aren’t supposed to be advocates for partisan ideologies. https://t.co/F9U4ND4Yb5 — Richard Grenell (@RichardGrenell) 22 декабря 2018 г.

​Der Spiegel announced this week that one of its star reporters had resigned due to committing journalistic fraud "on a grand scale". An internal investigation reportedly revealed that Claas Relotius, a 33-year old staffer who has won numerous accolades, including CNN Journalist of the Year in 2014, and who was named German Reporter of the Year earlier this month, has been inventing stories and faking interviews for several years.

Relotius’ cheating was apparently exposed when a colleague who worked with him on a story along the US-Mexican border became suspicious and tracked down two alleged sources who were quoted extensively in Relotius’ article, and who said that they actually had never met him.