The poster before the Austrian embassy in Berlin could be advertising fast food or washing powder. But, look closer, and you see the entrance to the Auschwitz concentration camp and the catchline: “Late, but not too late”.

Some 2,000 such posters popped up yesterday in Berlin, Hamburg and Cologne, offering a €25,000 reward for information that leads to the arrest and conviction of Nazi war criminals.

It marks the latest push by the Simon Wiesenthal Centre to locate as-yet unconvicted Third Reich war criminals.

The impetus for the campaign, dubbed “Operation Last Chance”, was the Munich trial of former SS guard John Demjanjuk for war crimes at the Sobibor camp in occupied Poland. Though he died last year before his conviction was finalised, it marked a watershed in Nazi trials.

In previous decades, German authorities had refused to open an investigation without concrete proof of a specific Nazi-era crime – often a difficult task given the regime’s industrial killing machine. But now German authorities have indicated a willingness to lower the legal hurdle to prosecutions, thus expanding the pool – if diluting the seniority – of potential Third Reich perpetrators still at large.

Dr Efraim Zuroff, the Simon Wiesenthal Centre’s chief Nazi hunter, concedes the strategy turns the focus on to smaller fish in the Nazi regime, but denies the lower rank of the 50 men and women he estimates are at large in Germany diminishes their guilt. The latest iteration of “Operation Last Chance”, in particular the reward component, has been attacked as “tasteless and impious” by the Israeli-born German historian Michael Wolfssohn. Posting a reward of €25,000 will make people wonder why such serious war criminals are “not worth more”, he argues, just as recent trials risk a backlash against Holocaust research by generating a wave of sympathy for elderly defendants.

Dr Zuroff argues that, if suspects are mentally and physically fit, they should go on trial. “When you look at these people you shouldn’t see old frail men and women trying to look as sick as possible,” he said, “but young people who, at the height of their strength, devoted their energies to murdering men, women and children. That is why they are in court, not because of how they look today.”

This “last chance” campaign can make up for the lack of Holocaust convictions in the past which, he argues, contributed to a sense of impunity felt by perpetrators of subsequent massacres from Srebrenica to Darfur. At yesterday’s launch Dr Zuroff, who describes his job as “one-third detective, one-third historian and one-third political lobbyist”, expressed doubts that the campaign can be expanded into other countries with Nazi pasts.

“I cannot think of a more suitable place for the poster in Berlin than the Austrian embassy,” he said. “In the last 30 years Austria has not succeeded in taking legal action against one Nazi war criminal. Do you think that is because there are no Nazi war criminals in Austria? That is a rhetorical question.”