"It's unsavory that our intelligence officials are using methods that were also used by the Stasi," the deputy parliamentary leader of the opposition Greens, Hans-Christian Ströbele, told the Leipziger Volkszeitung newspaper.
The feared secret police of former communist East Germany (GDR) notoriously tried to capture and store the body scents of political dissidents so that sniffer dogs could trace them.
Wolfgang Thierse, the deputy speaker of the Bundestag lower house of parliament, accused the authorities of going overboard and warned them to refrain from a "hysteria that could lead to a police state similar to the GDR."
Federal prosecutors confirmed on Tuesday that police took scent samples earlier in the month when they raided sites in northern Germany linked to suspected anti-globalization activists. But they denied that they wanted to use the samples to sniff out G8 protestors.
A spokesman said samples were taken from five or six suspects in order to compare these with physical evidence found at the scene of past arson attacks.
According to police, taking scent samples is as legal as taking fingerprints, and talks of the Stasi were exaggerated.
"'Stasi methods' clearly refers to … techniques such as denunciation, blackmail and torture, but not to what is a valid legal police practice," said Konrad Freiberg, the chairman of the Federal Police Union, in a statement on Wednesday.
Police should be able to use all methods "to preferably avert violence acts before they happen," he said.
However, Wolfgang Bosbach, the deputy chairman of the Christian Democratic parliamentary faction, said he found the whole practice of smell tracking "rather strange."
"You have a protester, the dog has a sniff and then he wags three times with his tail or barks -- what's supposed to happen then?" Bosbach said.
Left-wing groups have warned the police that the recent raids angered their supporters and would only heighten their resolve to demonstrate at the G8 summit being held in the northern coastal town of Heiligendamm from June 6 - 8.
Protesters are also upset over a ban on protests at the G8 venue and the nearby airport, and are taking legal action to attempt to overturn it.
It is believed that left-wing groups could be behind the torching on Tuesday of the car belonging to the editor of Bild, Germany's biggest-selling newspaper, and those of two businessmen last week.German authorities are expecting up to 100,000 activists to target the G8 summit being hosted by German Chancellor Angela Merkel. The leaders of the United States, Russia, Britain, France, Italy, Canada, and Japan are to attend.