Ognjen Kraus, who heads an umbrella association of Jewish groups, said they would "not attend" the official ceremony in Jasenovac on April 22 due to the ongoing trivialisation of the role of the Nazi-allied Ustasha regime and its symbols.
"Nothing was done (about it) in the past year," he told N1 television. "We cannot and will not ever reconcile with such politics."
The Ustasha persecuted and killed hundreds of thousands of ethnic Serbs, Jews, Roma and anti-fascist Croatians, all of whom boycotted last year's commemoration for Jasenovac victims over a resurgence in pro-Ustasha sympathies.
In January, the Jewish community also snubbed the official ceremony for International Holocaust Remembrance Day for the same reasons.
Around three-quarters of the Jewish community, which numbered around 40,000, were killed by the Ustasha. They now make up less than one percent of Croatia's population of 4.2 million.
Central to the issue is a memorial plaque with an Ustasha slogan that was unveiled in Jasenovac in November by former paramilitaries to honour fellow fighters killed in the area at the start of Croatia's 1990s independence war.
Ethnic Serbs said they would attend this year's commemoration if the slogan was removed.
Conservative Prime Minister Andrej Plenkovic, who came to power following snap elections in October, has pledged to move away from extremism.
Under the previous centre-right government, there was a growing climate of intolerance which included nostalgia for a pro-Nazi past and attacks on independent media and minorities, notably ethnic Serbs.
Critics say the current administration has not done enough to move away from its predecessor's policies.
In January, a Croatian school refused to display an exhibition on Jewish diarist Anne Frank because it included panels on the Ustasha crimes.
And the next month, dozens of a far-right activists marched through downtown Zagreb chanting a pro-Nazi salute. Their leader was eventually arrested.
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