LUTON, England — When Mohammed Qurban stood outside the Jamia mosque in the heavily Muslim Bury Park district on Tuesday and spoke anxiously about Britain’s record-high levels of immigration, he was reflecting a powerful undercurrent that could help tip victory in dozens of constituencies in Thursday’s general election to the main opposition groups vying with the governing Labour Party for power, the Conservatives and the Liberal Democrats.

“I think this country is coming overpopulated, too many people coming in from everywhere, especially Europe,” Mr. Qurban said, as fellow worshipers nodded in assent. In particular, he said, thousands of Poles in Luton were taking jobs from the children and grandchildren of a previous generation of immigrants like himself, those who arrived from Pakistan in one of Britain’s early waves of migration in the 1960s.

The conversation with Mr. Qurban, and at least a dozen others like it with Muslims in Luton, captured a shift of potentially far-reaching significance. The most strident opponents of large-scale immigration have traditionally been white, native-born Britons, and their favorite target immigrant blacks and Asians, particularly Muslims.

The incongruity was not lost on Mr. Qurban, 56, a rental agent who seemed keen to separate himself from the skinheads and others whose anti-immigrant agitation has sometimes turned violent. “This is my town, this is my bread-and-butter,” he said. “I’m a law-abiding citizen, never crossed the line, that is definitely out of order. The Poles have a problem at home as we do in Pakistan, no jobs, no money. I want to go along with them. But definitely, it’s up to the government to put a cap on it.”