“Family tree research is pure racism and a scandal,” according to German politicians disturbed by a police probe into Stuttgart riot suspects.

The comments came as part of a backlash over a police investigation into riots which saw 19 officers injured, several state vehicles destroyed, and more than 30 businesses damaged.

Anger broke out amongst left-wing political forces after it was announced that police would look into suspects’ family backgrounds and whether or not their parents were born in Germany.

“Family tree research is pure racism and a scandal that needs to be immediately stopped,” said Left party parliamentary head, Dietmar Bartsch speaking to RedaktionsNetzwerk Deutschland (RND) on Sunday.

The leftist party chairman also demanded that interior minister Horst Seehofer approve an investigation into allegations of racial profiling by police in Germany.

Other politicians echoed the Left party chairman, with figures from the Social Democratic Party (SPD), Greens, and the liberal Free Democratic Party speaking out against the so-called “genealogy research”.

German public broadcaster Deutsche Welle said that left-wing members of the public took to social media to denounce “family tree research”. DW reported that “many social media users [drew] parallels to the Nazi regime, which used ancestry research to track down people with Jewish bloodlines during the Holocaust”.

On Twitter, FDP MP Johannes Vogel stated: “Transparency about nationalities, sure, but first and second-class Germans don’t exist. And it doesn’t have anything to do with solving crimes. This poison needs to be removed from people’s minds!”

A spokesman for the police explained that research into the suspects’ family backgrounds was in order to determine the living and family circumstances of riot perpetrators, according to a report from Tagesschau. The news service said authorities denied that the term “family tree research” was ever used at a council meeting on the subject.

Further, the Federal Government also rejected that the term had been used, with government spokesman Steffen Seibert stating that “it is a historically charged and inappropriate word”.

However, he stressed that there were “significant crimes” that needed to be solved in Stuttgart following the riots, in which there was mass looting and police said that half of the hundreds of people arrested had German citizenship while the other half were foreign nationals.

In a statement, police said it was unclear whether a number of suspects with German citizenship have an immigrant background, explaining: “For this reason, in individual cases the nationality of the parents — and only the parents — of the suspects being determined through inquiries at the registry office in order to clarify whether there is a migrant background.”

It argued such details were required for the criminal investigations taking place, and additionally would be helpful for knowing what sorts of youth programmes the state should provide in order to prevent recurrences of riots in the future.

“In order to be able to guarantee successful prevention work in the long term, tailor-made concepts are needed that take into account personal living circumstances as well as a potential migrant background,” added the statement.

The populist Alternative for Germany (AfD) linked the riots, which took place last month, on mass immigration to the country, asserting it was “no coincidence” that violence in Stuttgart “hit a city with a 44 per cent migrant population”.

“Without a political paradigm shift, such scenes will repeat themselves in Stuttgart and in other German cities. What we need is consistently controlled immigration, more police and a crackdown on the judiciary against such criminals. The old parties, however, seem to lack the strength and the will to do so,” the party said.