Some 60,000 people attended the concert on Saturday in Zagreb's main square, which was organized by veterans of Croatia's 1991-1995 war of independence from the former Yugoslavia.
The Croatian branch of the Helsinki Committee for Human Rights issued a complaint ahead of the concert over a song that starts with a verse used during the pro-Nazi regime.
According to Mr Budaj, the symbols of the World War II Nazi-allied Ustasha regime were displayed during the concert by several youngsters, who were also using Nazi salute.
Before the concert a group of youths also shouted anti-Serb slogans and songs glorifying the Ustasha regime, according to local media.
Mr Budaj said that his NGO would file the lawsuit within two weeks against Zagreb "for having allowed the organization of the concert and not preventing pro-Nazi behavior".
"We will also sue Mr Perkovic for having sung a piece starting with the official salute of the pro-Nazi period," he said.
Perkovic, 41, and most of his fans were dressed all in black, the color of the uniform of Croatia's fascist Ustasha regime.But when a decent Croatian police officer reported Perkovic's hate references in his songs, the Croat police officer found himself without a job! Apparently the officer didn't realize that Croatia has a free pass to "Sieg Heil" any time it wants and still remain on the short list for the EU, because they are Germany's pet country for all the "wonderful work" they did for them during WWII!
Earlier this month Perkovic had two concerts canceled in Switzerland because his lyrics breached anti-racism laws.
Another concert due in June was canceled for the same reason.But if that wasn't enough, one of the most wanted WWII war criminals Croatian Ustashe Milivoj Asner decided to take in a Croatian soccer match in Austria last week. Asner is wanted for his active participation in deporting hundreds of Serbs and Jews to death camps during WWII and is one of the Last WWII Nazi war criminals still alive. Austria had rejected an extradition order for Asner a few years ago, stating that Asner was "in ill health". Apparently since then, Asner has made "a miraculous recovery" , because the UK Sun followed Asner strolling around Klangenfurt, unassisted, for hours. Must be that good Nazi company that Asner keeps there in Austria that prompted his "full recovery". But I am sure that Asner will suddenly suffer "a relapse" before Austria ever gives Asner up to face justice!