Senator JD Vance of Ohio, the Republican vice-presidential nominee, on Friday defended his past unsubstantiated claims about immigration in which he suggested that early waves of Italian, Irish and German immigration led to higher crime and interethnic conflict, by citing the movie “Gangs of New York.”

At a campaign event before the Milwaukee Police Association, Mr. Vance was asked about the comments — which have resurfaced in recent days — from a 2021 interview with the far-right podcaster Jack Murphy, and whether he would have prescribed the kind of mass deportations then that he and former President Donald J. Trump have made central to their platform now.

Mr. Vance mostly skirted the question on removals, but he stood by his comments on crime and ethnic and interethnic conflict, pointing to the Martin Scorsese film that depicts gang violence between Irish migrants and nativist Protestant Americans.

“Well, first of all, I also said there were a lot of benefits to that wave of immigration, but has anybody ever seen the movie ‘Gangs of New York’? That’s what I’m talking about,” he said. “We know that when you have these massive ethnic enclaves forming in our country, it can sometimes lead to higher crime rates.”

Later, he added: “What happens when you have massive amounts of illegal immigration? It actually starts to create ethnic conflict. It creates higher crime rates.”

Asked to provide evidence for the claims, a campaign spokeswoman pointed to a report from an anti-immigration think tank that argues crimes committed by immigrants are underestimated because many crimes go unreported and to a rise in violence in Minnesota that the authorities have attributed to a rivalry between St. Paul and Minneapolis East African gangs.