Mr. Tajani has apologized several times, but he also insists that he was misinterpreted and that it was not his intention to make territorial claims.

“I was referring to the Istrian and Dalmatian Italian-language exiles, their children and grandchildren,” he said in one of his apologies. He was referring to Italians who were forced from the regions after Italy surrendered to allied forces at the end of World War II.

Mr. Tajani, who has refused to resign, declined a request for an interview.

After the end of World War II, ethnic Italians living in the coastal areas of Istria and Dalmatia — even those who had called those areas home for centuries — were viewed as collaborators with fascist Italy; most were either expelled or killed.

Some were thrown into deep limestone caves and pits that dot the Adriatic Coast. Many people in Italy refer to the mass killings simply as “foibe,” or caves. A joint Italian-Slovenian historical committee estimated that as many as 4,000 ethnic Italians were killed.

“In Italy, for the past 20 to 25 years, there has been a reinterpretation of their history — especially as it concerns Rijeka and Istria,” said Franko Dota, a Croatian historian. Rijeka is a city in Croatia.

“During the Cold War, the issue of territories was not discussed especially when it was associated to fascism and the fact that Italy was on the wrong side of history,” Mr. Dota said. “After the Cold War, it became easier for nationalist historians to promote a different interpretation of what they saw as injustices perpetrated against Italians in these areas.”

But that narrative, Mr. Dota and others say, ignores the oppression endured by Slovenians and Croatians when Italy controlled their territory. “The experience people remember most from this period is that of Italian fascist expansionism, which many know as a period of repression over the Slovene and Croat population,” he said.