Ukraine will not be able to join the European Union unless it recognises the World War 2 Volhynia killings as genocide, Polish Deputy Prime Minister Wladyslaw Kosiniak-Kamysz said on August 26.

At a press briefing, Kosiniak-Kamysz said Ukraine “will have no chance" of joining the European Union without acknowledging the atrocities committed in Volhynia in 1943. 

“The genocide in Volhynia is one of the most terrible acts of terror against a nation in the history of our civilisation, Ukraine must answer for this, there must be monuments, exhumation, a dignified burial. We will never back down from this," Kosiniak-Kamysz said.

At the same time, he stressed that withholding support from a neighbour at war “is contrary to the security interests of the Polish state” and that helping Ukraine “also means building a secure Poland.”

The Volhynia massacres, in which the Ukrainian Insurgent Army killed tens of thousands of Polish civilians in 1943, remain the most contentious chapter in relations between the two countries. 

Estimates suggest between 60,000 and 90,000 Poles were killed, while reprisals by Poles claimed 10,000 to 20,000 Ukrainian lives. Warsaw classifies the events as genocide. Kyiv, however, regards the nationalist movement responsible for the killings as central to its own statehood narrative, making an official apology politically fraught.

Polish President Karol Nawrocki has also pressed the issue. In July, he urged Ukrainian President Volodymyr Zelensky to authorise large-scale exhumations of Polish victims, a process that has been ongoing since earlier this year. 

On August 25, Nawrocki vetoed a bill extending assistance for Ukrainian refugees, arguing that benefits should be limited to those working in Poland. His draft proposals also included tougher penalties for illegal border crossings, longer waiting times for citizenship, and criminalising Ukrainian nationalist symbols alongside Nazi and Communist ones.

Ukraine said it would “react” if the symbols were banned.

The Polish government, which is locked in a fierce political battle with Nawrocki, said the veto was a gift to Russian propaganda trying to weaken Poland’s resolve to help Ukraine, as it is fighting for independence.

Nawrocki, a conservative aligned with the opposition Law and Justice party, narrowly won Poland’s presidential election on June 1. A historian by training, Nawrocki has pledged solidarity with Ukraine against Russia while at the same time highlighting disputes over wartime history and signalling opposition to Ukraine’s EU and Nato ambitions.

Polish resistance to Ukraine’s accession is not new. In September last year, Prime Minister Donald Tusk said Kyiv would not receive Warsaw’s backing for EU membership until it “meets Poland’s expectations” on dealing with the Volhynia atrocities. 

Reconciliation over history is part of the “cultural-political standards” of the EU, comparing the process to Franco-German rapprochement after the Second World War, Tusk said at the time.

Ukraine’s then-foreign minister Dmytro Kuleba countered that debates over past atrocities should be left to historians, as digging into history while fighting Russia risked souring relations, and instead urged both nations to focus on the future. His comments drew a negative reaction in Warsaw.

The dispute over history feeds into wider political battles. The EU is not united on Ukraine’s membership bid. Hungarian Prime Minister Viktor Orban, who has long opposed the move, has faced fresh pressure since a call from US President Donald Trump last week, nurturing hopes - both in Brussels and Kyiv - that he might back down.

Still, Orban posted online that “Ukraine’s membership in the European Union does not provide any security guarantees” and warned that linking the two was “unnecessary and dangerous.”