Poland’s prime minister canceled plans for his country to send a delegation to a meeting in Jerusalem on Monday after the acting Israeli foreign minister said that Poles “collaborated with the Nazis” and “sucked anti-Semitism with their mothers’ milk.”

The Polish pullout triggered the collapse of a planned summit of Israeli Prime Minister Benjamin Netanyahu with leaders of four Central European nations known as the Visegrad group.

With the Hungarian and Slovak prime ministers already in Israel, bilateral meetings will take place instead, according to announcements by Czech Prime Minister Andrei Babis and Israeli Foreign Ministry spokesman Emmanuel Nahshon.

Netanyahu had touted the meeting as an important step in his outreach to the countries of Central Europe, which have pro-Israel governments that he is counting on to counter the criticism Israel typically faces in international forums.

The developments mark a new low in a bitter conflict between Poland and Israel over how to remember and characterize Polish actions toward Jews during the German occupation of Poland in World War II.

Polish Prime Minister Mateusz Morawiecki had already announced Sunday that he was pulling out of the meeting after a comment by Netanyahu last week about Polish cooperation with Nazis.

Morawiecki canceled Polish participation altogether after comments made by Israel’s acting foreign minister, Israel Katz, which he denounced as “racist” and “absolutely unacceptable.”

Poland’s Foreign Ministry also summoned the Israeli ambassador, Anna Azari, to demand a second set of clarifications in recent days.

Monday’s development marks a deterioration of a spat that began last Thursday when Netanyahu said: “Poles cooperated with the Nazis.”

Netanyahu’s office said he was misquoted. The Polish government first summoned the Israeli ambassador on Friday but said it was not satisfied with the explanation of the Israeli leader being quoted incorrectly.

Katz, made his remarks Sunday in an interview on Reshet 13 TV.

“I am the son of Holocaust survivors,” he said, in his first day in the new job. “The memory of the Holocaust is not something to compromise about. It is obvious. We will not forget, and we will not forgive.”

He then vowed that no one would change the historical truth of what happened.

“Poles collaborated with the Nazis, definitely. Collaborated with the Nazis. As (former Israeli Prime Minister) Yitzhak Shamir said — his father was murdered by Poles — he said that from his point of view, they sucked anti-Semitism with their mothers’ milk. You can’t sugarcoat this history,” he said.

Poland was the first occupation of Adolf Hitler’s regime and never had a collaborationist government. Members of Poland’s resistance and government-in-exile struggled to warn the world about the mass killing of Jews, and thousands of Poles risked their lives to help Jews.

However, Holocaust researchers have collected ample evidence of Polish villagers who murdered Jews fleeing the Nazis, or Polish blackmailers who preyed on the Jews for financial gain.