Israeli PM Benjamin Netanyahu has sharply rebuked his Polish counterpart for saying that Jews were among the perpetrators of the Holocaust.
He said the remarks by Mateusz Morawiecki at the Munich Security Conference were "outrageous".
Mr Netanyahu said they showed "an inability to understand history".
The dispute comes weeks after Israel condemned a new Polish law making it illegal to accuse the Polish nation or state of complicity in Nazi crimes.
The legislation was signed into law by President Andrzej Duda but also referred to the country's highest court to consider its constitutionality.
What did Mr Morawiecki say in Munich?
He was responding to an Israeli journalist who asked if anyone who said there were Polish collaborators in the Holocaust would be considered a criminal in Poland under the new law.
Mr Morawiecki said: "It's extremely important to first understand that, of course, it's not going to be punishable, not going to be seen as criminal to say that there were Polish perpetrators - as there were Jewish perpetrators, as there were Russian perpetrators, as there were Ukrainian.... not only German perpetrators."
Mr Morawiecki has not publicly responded to Mr Netanyahu's criticism.
What does the new Polish law state?
It says that "whoever accuses, publicly and against the facts, the Polish nation, or the Polish state, of being responsible or complicit in the Nazi crimes committed by the Third German Reich… shall be subject to a fine or a penalty of imprisonment of up to three years".
But it adds the caveat that a person "is not committing a crime if he or she commits such an act as part of artistic or scientific activities".
The country has long objected to the use of phrases like "Polish death camps", which suggest the Polish state in some way shared responsibility for camps such as Auschwitz. The camps were built and operated by Nazi Germany after it invaded Poland in 1939.
But the more contentious point raised by the law is whether it will outlaw references to acts of individual complicity by Poles with the Nazis - something historians say there is clear evidence for.
How did Israel respond?
The Israelis have been furious about the legislation, which Mr Netanyahu has described as an attempt to rewrite history and deny the Holocaust.
Deputies from across Israel's often fractious political spectrum have united to denounce it.
Following the passage of the law in the Senate, Israel's Foreign Ministry asked to postpone the visit of a senior Polish official.
Now, Israeli MPs are backing a bill that would expand Israel's existing Holocaust denial laws to include a five-year jail sentence for anyone denying or minimising the role of Nazi collaborators, including Poles, in crimes committed in the Holocaust.
The amended law would also give legal aid to any Holocaust survivor telling their story who is prosecuted in a foreign country.
What happened in World War Two?
Poland was attacked and occupied by Nazi Germany. Millions of its citizens were killed, including three million Polish Jews in the Holocaust.
Six million Jews were killed in the Holocaust overall.
More Poles have been honoured by Israel for saving the lives of Jews during the war than any other nation.
However, historians say others were complicit by acts such as informing on Jews in hiding for rewards, and participating in Nazi-instigated massacres including in Jedwabne where hundreds of Jews were murdered by their neighbours.
A historian and well-known "Nazi-hunter" at the Simon Wiesenthal Center, Efraim Zuroff, says the number of collaborators runs into "many thousands".