BRUSSELS — One of the seminal slogans of the 20th century was the historic refrain “Never again!” This cry that rose from the ashes of the Holocaust was meant to ensure that there would be no repeat of the greatest tragedy in modern European history.

The refrain remains hollow if it remains a theoretical verbiage utilized during speeches and ceremonies but lacking any real intent and action.

In recent years, a seemingly long dormant ideology returned to a semblance of power for the first time since the unconditional surrender of the German forces on May 8, 1945. For the first time in well over six decades, political parties that require members to be of “Aryan origin,” have full armed and open-fisted salutes, have logos distinctly resembling the swastika and call for a census of Jews are back in Europe.

These elements are no longer consigned to the beer halls, isolated farm retreats or the margins of European political discourse. They are moving closer and closer to the mainstream.

In fact, this newfound political confidence is reflected in the street, where more and more Jews are being physically and verbally attacked in the open.

The Golden Dawn party in Greece, Jobbik in Hungary and Svoboda in Ukraine are just three examples of European political parties that have moved well beyond the historic far right and still unacceptable discourse of those like Le Pen’s National Front and the Freedom Party in Austria.

We appear to be entering a new phase in European political history that has extremely worrying parallels with the past. Of course, many will argue that none of these parties currently have great power.

But at what point will their power be too much? It’s a question that all decision makers, opinion shapers and law enforcement agencies in Europe must ask. Not in a theoretical sense, but in a very real practical sense.

The Jewish people and other minorities who are in the direct line of fire from this maleficent hate have no doubts that this threshold already has passed, and it is having a very real practical effect on the streets. A recent survey found that 63 percent of Hungarians are willing to affirm their anti-Semitism with no shame.

On Sunday, the international community observed International Holocaust Remembrance Day to remember the victims of the Holocaust and learn its lessons. A few days prior, I visited the seat of European governance, the European Parliament, which was the joint recipient of the recent Nobel Prize for Peace, along with other European Union institutions. Along with many others, I lauded the Nobel for the European Union’s commitment to peace and its success at unifying a continent that has known so much bloodshed.

However, as Europeans, we cannot afford to rest on our laurels and claim that a lack of war or conflict means that the European Union has succeeded in creating a harmonious and peaceful continent that can prevent future catastrophes.

As the number of Holocaust survivors begins to dwindle, many are witnessing something that would have been unbelievable to them only a few short years ago: The new groups, rapidly increasing in popularity, are emulating and co-opting the policies and ideology of those who murdered their families and brought to them untold suffering.

There are too many Europeans, especially those among its leadership, who remember the death and destruction that follows the Nazi ideology and we, as Europeans, should do everything we can to rid ourselves of this force that again tries to lay a dark shadow on our continent.

We call on all figures in Europe –media, cultural or academic – to use their platforms to assist the ridding of this disease. European politicians as a moral mass must adopt stricter legislation proscribing groups that promote hate, discrimination and racism from European political institutions. There must also be a demand for tougher enforcement and punishment, and the strengthening of education toward tolerance.

Some eight decades ago, the National Socialist Movement caught many by surprise, and most did not fully comprehend or believe that it would be willing or able to fulfill its genocidal and destructive platform. Living with this dark history in our relatively recent lifetime, we have no similar excuses. We know what this ideology seeks, we know what this racist movement aspires to and we cannot let it get a foothold again on our continent.

Just as eight decades ago, the Nazi ideology was able to take advantage of a financial recession, so we face similar economic challenges. This is when we must be at our most vigilant. We must beat back the advances of this ideology — not for the victims of the past but for the possible victims in the future. If we do not, then “Never again!” will remain a hollow term utilized during speeches and ceremonies.

As the prominent Holocaust historian Yehuda Bauer said, “Thou shalt not be a victim, thou shalt not be a perpetrator, but, above all, thou shalt not be a bystander.”

(Moshe Kantor is president of the European Jewish Congress and co-chairman of the European Council on Tolerance and Reconciliation.)