The British vote to leave the European Union was motivated by several factors and in nearly two-thirds of the seats held by the Labour Party (and in no less than four-fifths of those located in the North of England and the Midlands) a majority of voters voted to leave the EU − but across Britain as a whole, 63% of those who voted Labour in 2015 and who cast a ballot in the EU referendum, voted to Remain.
The Economist was more specific on how immigration impacted the vote: "Where foreign-born populations increased by more than 200% between 2001 and 2014, a Leave vote followed in 94% of cases. The proportion of migrants may be relatively low in Leave strongholds such as Boston, in Lincolnshire (where 15.4% of the population are foreign-born). But it has grown precipitously in a short period of time (by 479%, in Boston’s case). High levels of immigration don’t seem to bother Britons; high rates of change do."