On Sunday, a European media investigation, which included Germany's broadcasters NDR, WDR and the Suddeutsche Zeitung newspaper, showed that the Danish Defense Intelligence Service (FE) cooperated with the US intelligence operations that targeted the highest-ranking European officials, including Chancellor Angela Merkel, from 2012 to 2014.
"Politically, I consider this a scandal," Steinbruck, a then-chancellor candidate from the Social Democratic Party of Germany, said in an interview with the German members of the research team, as quoted by the broadcaster Deutsche Welle.
The broadcaster reports that neither Merkel nor German President Frank-Walter Steinmeier was aware of Denmark's involvement in spying operations against them. The chancellor's spokesperson said that Merkel had been informed about the situation.
Former US intelligence officer Edward Snowden commented on the reports by accusing US President Joe Biden, who served as the vice president in the Barack Obama administration, when the surveillance was taking place, of being involved in the scandal.
"Biden is well-prepared to answer for this when he soon visits Europe since, of course, he was deeply involved in this scandal the first time around. There should be an explicit requirement for full public disclosure not only from Denmark, but their senior partner as well," Snowden tweeted.
In 2013, US whistleblower Edward Snowden released documents suggesting that Merkel and her entourage had been spied on by the US intelligence services for years. The German authorities launched a probe into the claims, which was later dropped over the lack of evidence to mount a legal action.